diff --git a/CHANGELOG.md b/CHANGELOG.md
index a0c9cb0..e5317cd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,7 +20,11 @@ folgen [Semantic Versioning](https://semver.org/lang/de/). Die Version steht in
 ### Verbessert
 - Schnellzugriff: `search`, `seek`, `delete` und `update.rdb` lesen bei `-mh`, `-mi` und `-mr` nur noch den Indexeintrag und den einen Satz (Seek auf Byte-Positionen, bei `.i` Halbierung über die Datei), nicht mehr Tabelle und Index vollständig. `Data` liest die Zeilen erst, wenn eine Methode alle braucht.
 - Die Hashfunktion ist FNV-1a statt der Bytesumme. Vorher fielen 3000 fünfstellige Nummern in 30 Plätze (größter Eimer 223), jetzt liegt der größte Eimer bei etwa 4. **Hashindizes (`.h`) müssen neu gebaut werden** (`index -mh`).
-- `total`, `mean`, `subtotal` und die /act-Befehle rechnen mit `BigDecimal` statt `Float`: `0.1 + 0.2 + 0.7` ergibt `1.0`, Beträge summieren sich auf den Rappen genau, und es wird kaufmännisch gerundet (halb auf).
+- `total`, `mean`, `subtotal` und die /act-Befehle rechnen exakt mit `Rational` statt `Float`: `0.1 + 0.2 + 0.7` ergibt `1.0`, Beträge summieren sich auf den Rappen genau, und es wird kaufmännisch gerundet (halb auf).
+
+- `bin/rdb` startet mit `ruby --disable-gems`: jeder Befehl ist in etwa doppelt so schnell gestartet (ca. 85 statt 170 ms), weil RubyGems nicht geladen wird. `rdb` braucht nur die Standardbibliothek.
+- Die Tests laufen parallel (`parallelize_me!`; `MT_CPU=1` für nacheinander). Zusammen mit dem schnelleren Start dauert die Suite 21 statt 70 Sekunden.
+- Intern: Hilfsfunktionen der Befehlsdateien liegen in `Rdb::Helpers` statt auf `Object`, die Konstanten (`STATS`, `TERM_CAPS` ...) in `Rdb`. Kopf- und Strichzeile entstehen an einer Stelle (`Table.head_text`, `dash_cells`, `headed?`), `awk` baut auf `awk_text` auf.
 
 ### Sicherheit
 - `report`: Spaltenwerte in `<!befehl <Spalte>!>` wurden unmaskiert in einen Shell-Aufruf eingesetzt, eine Zelle konnte so Befehle ausführen. Sie werden jetzt mit `Shellwords.escape` eingesetzt.
diff --git a/README.md b/README.md
index 49a8c30..ccd6859 100644
--- a/README.md
+++ b/README.md
@@ -246,7 +246,7 @@ er nicht mehr passt (außer mit `-a`). Beide halten die Indizes aktuell.
   die Hashtabelle `.h` hat 2n statt 2n+1 Plätze (Hashfunktion FNV-1a), und in `.i` steht der
   Schlüssel vor dem Offset statt dahinter. Alte /rdb-Indizes und `.h`-Dateien früherer
   Versionen dieses Nachbaus muss man neu bauen.
-- Summen, Mittelwerte und /act-Beträge sind Dezimalzahlen (`BigDecimal`), gerundet wird halb auf.
+- Summen, Mittelwerte und /act-Beträge sind Dezimalzahlen (`Rational`), gerundet wird halb auf.
 - Dateien, die kein UTF-8 sind, liest `rdb` als Latin-1 und schreibt sie als UTF-8. Fehler
   erscheinen als eine Zeile; mit `RDB_DEBUG=1` kommt der Ruby-Backtrace. Werte mit Tab oder
   Zeilenumbruch lehnen `append`, `enter`, `replace` und `ve` ab.
diff --git a/bin/rdb b/bin/rdb
index c9f2ad6..ac2c119 100755
--- a/bin/rdb
+++ b/bin/rdb
@@ -1,8 +1,10 @@
-#!/usr/bin/env ruby
+#!/usr/bin/env -S ruby --disable-gems
 # frozen_string_literal: true
 
 # rdb -- every /rdb command is this one program, looking at the name it was
 # called by. `row`, `column`, `total` ... are symlinks to it (`rdb install`).
+# --disable-gems: rdb needs only the standard library, and skipping RubyGems
+# makes each command start about twice as fast.
 
 require_relative '../lib/rdb'
 
diff --git a/doc/review.md b/doc/review.md
index 76d6a57..a2a14fe 100644
--- a/doc/review.md
+++ b/doc/review.md
@@ -81,22 +81,26 @@ Index ohne Entsprechung in der Suche offen.
 2. **Schlechte Hash-Funktion — Behoben** (FNV-1a, größter Eimer 4). Ursprünglich: ([fast.rb:68](../lib/rdb/fast.rb)):
    `bytes.sum % slots`. Bestätigt: 3000 fünfstellige Nummern landen in 30 Slots,
    größter Bucket 223. Abhilfe: FNV-1a o. Ä., Primzahl-Slotzahl.
-3. **Geld in `Float` — Behoben** (`BigDecimal` in `total`/`mean`/`subtotal` und /act). Ursprünglich: ([act.rb:11](../lib/rdb/cmd/act.rb), `to_f` im /act-Teil
+3. **Geld in `Float` — Behoben** (`Rational` in `total`/`mean`/`subtotal` und /act). Ursprünglich: ([act.rb:11](../lib/rdb/cmd/act.rb), `to_f` im /act-Teil
    und in `total`). Abhilfe: `BigDecimal` oder ganzzahlige Rappen.
-4. **awk-Brücke** ([env.rb:119-138](../lib/rdb/env.rb)): ganze Tabelle als String
+4. **awk-Brücke — bewusst offen.** `awk` und `awk_text` teilen sich jetzt den Aufruf. Streaming
+   und ein eigener Ausdrucksparser wären ein Umbau mit Verhaltensrisiko (awk-Syntax ist
+   dokumentierte Schnittstelle). Ursprünglich: ([env.rb:119-138](../lib/rdb/env.rb)): ganze Tabelle als String
    durch `capture3`, kein Streaming; handgeschriebener Parser erkennt Strings und
    Regexe heuristisch (`prev`) und hängt vom awk-Dialekt ab.
-5. **Globale Methoden auf `Object`** (`fast_opts`, `lock_file`, `num`, `money`,
+5. **Globale Methoden auf `Object` — Behoben** (`Rdb::Helpers`, Konstanten in `Rdb`). Ursprünglich: (`fast_opts`, `lock_file`, `num`, `money`,
    `ask`, `need`, `show_record` …). In ein Modul kapseln und in `Env` einbinden.
-6. **Doppelter Code.** `awk`/`awk_text`; Schlüsseltabellen-Parsing in `fast_opts`/
+6. **Doppelter Code — Behoben** (`Table.head_text`, `dash_cells`, `headed?`; `awk` über `awk_text`). Ursprünglich: `awk`/`awk_text`; Schlüsseltabellen-Parsing in `fast_opts`/
    `key_columns`; von Hand gebaute Kopf-/Strichzeilen trotz `Table.dash_row`.
-7. **Tests.** Laufzeit ca. 66 s wegen eines Ruby-Prozesses pro Test. Fehlerfälle
+7. **Tests — Behoben** (Suite 70 s → 21 s). Parallel, und `bin/rdb` startet mit `--disable-gems` (ca. 85 statt
+   170 ms je Befehl). Fehlerfälle haben jetzt Tests. Den Rest der Zeit braucht
+   `test_testall_runs_demo_script` (rund 300 Befehle nacheinander). Ursprünglich: Laufzeit ca. 66 s wegen eines Ruby-Prozesses pro Test. Fehlerfälle
    (Encoding, Tab in Wert, Locks, Editor) nicht abgedeckt; Tests direkt gegen
    `Rdb.run` im Prozess wären schneller.
-8. **Repo.** `demo/fact.pl`, `fact_lc.pl`, `rule.pl` sind ungetrackt;
+8. **Repo — offen, Entscheidung beim Autor.** Ursprünglich: `demo/fact.pl`, `fact_lc.pl`, `rule.pl` sind ungetrackt;
    `demo/testall.old` (1187 Zeilen) wäre als Golden-File-Test besser gepflegt.
 
 ## Empfohlene Reihenfolge
 
-Schwachstellen, Fehler und Verbesserung 1–3 sind erledigt. Offen sind 4–8: die
-awk-Brücke, globale Methoden auf `Object`, doppelter Code, Testlaufzeit, Repo-Aufräumen.
+Schwachstellen, Fehler und Verbesserungen 1–3 und 5–7 sind erledigt.
+Offen: die awk-Brücke (4, bewusst) und das Repo-Aufräumen (8).
diff --git a/lib/rdb.rb b/lib/rdb.rb
index ad54bc9..50aba9e 100644
--- a/lib/rdb.rb
+++ b/lib/rdb.rb
@@ -3,7 +3,6 @@
 # A Ruby re-creation of /rdb, the relational database tools Mark Williams
 # Company sold for COHERENT (~1991).
 
-require 'bigdecimal'
 require 'open3'
 require 'date'
 require 'tmpdir'
@@ -33,6 +32,25 @@ module Rdb
       hits.first
     end
 
+    # Exact decimal arithmetic with Rational (core Ruby, so bin/rdb can start
+    # without RubyGems): 0.1 + 0.2 is 0.3 and money adds up to the cent.
+    def decimal(str)
+      s = str.to_s.strip
+      return 0r if s.empty?
+
+      Rational(s.match?(NUM) ? s.sub(/\.\z/, '') : s.to_f.to_s)
+    end
+
+    # num with dec places, rounded half up ("%.2f" rounds the binary value).
+    def fixed(num, dec)
+      r = num.is_a?(Float) ? Rational(num.to_s) : num.to_r
+      r = r.round(dec, half: :up)
+      return r.to_i.to_s if dec.zero?
+
+      digits = (r.abs * 10**dec).to_i.to_s.rjust(dec + 1, '0')
+      "#{'-' if r.negative?}#{digits[0...-dec]}.#{digits[-dec..]}"
+    end
+
     def die(msg)
       abort "#{File.basename($PROGRAM_NAME)}: #{msg}"
     end
diff --git a/lib/rdb/cmd/access.rb b/lib/rdb/cmd/access.rb
index 66df065..dca4afb 100644
--- a/lib/rdb/cmd/access.rb
+++ b/lib/rdb/cmd/access.rb
@@ -6,54 +6,57 @@
 require 'stringio'
 require_relative '../fast'
 
-# Parse the common fast-access options. Stops at the first non-option, which
-# is left in args; returns the option hash.
-def fast_opts(args)
-  o = { m: 's', h: false, l: false, s: false, x: false, exact: false, a: false, v: false, o: nil }
-  until args.empty?
-    a = args.first
-    case a
-    when /\A-m([bhirs]?)\z/ then o[:m] = Regexp.last_match(1).empty? ? 's' : Regexp.last_match(1)
-    when '+x' then o[:exact] = true
-    when '-o' then args.shift; o[:o] = args.first
-    when /\A-[hslxav]+\z/ then a[1..].each_char { |c| o[c.to_sym] = true }
-    else break
+module Rdb
+  module Helpers
+    # Parse the common fast-access options. Stops at the first non-option, which
+    # is left in args; returns the option hash.
+    def fast_opts(args)
+      o = { m: 's', h: false, l: false, s: false, x: false, exact: false, a: false, v: false, o: nil }
+      until args.empty?
+        a = args.first
+        case a
+        when /\A-m([bhirs]?)\z/ then o[:m] = Regexp.last_match(1).empty? ? 's' : Regexp.last_match(1)
+        when '+x' then o[:exact] = true
+        when '-o' then args.shift; o[:o] = args.first
+        when /\A-[hslxav]+\z/ then a[1..].each_char { |c| o[c.to_sym] = true }
+        else break
+        end
+        args.shift
+      end
+      o
     end
-    args.shift
-  end
-  o
-end
 
-def need_index(table, method)
-  suffix = Rdb::Fast::SUFFIX[method]
-  return unless suffix && !File.exist?(table + suffix)
+    def need_index(table, method)
+      suffix = Rdb::Fast::SUFFIX[method]
+      return unless suffix && !File.exist?(table + suffix)
 
-  Rdb.die("no index #{table}#{suffix}: run index -m#{method} #{table}")
-end
+      Rdb.die("no index #{table}#{suffix}: run index -m#{method} #{table}")
+    end
 
-# The key columns and, unless keys come from the terminal, the keys. Without key
-# columns on the command line a key table names them in its head line
-# (handbook p. 105: "search -mh mailtable < name"); otherwise the first column.
-def key_columns(args, data)
-  return [args.empty? ? [data.head[0]] : args, nil] if $stdin.tty?
+    # The key columns and, unless keys come from the terminal, the keys. Without key
+    # columns on the command line a key table names them in its head line
+    # (handbook p. 105: "search -mh mailtable < name"); otherwise the first column.
+    def key_columns(args, data)
+      return [args.empty? ? [data.head[0]] : args, nil] if $stdin.tty?
 
-  text = $stdin.read.to_s
-  lines = text.lines.map { |l| l.chomp("\n") }
-  cols = args
-  if cols.empty?
-    keyed = lines.size >= 2 && Rdb::Table.dash_line?(lines[1].split("\t", -1))
-    cols = keyed ? lines[0].split("\t", -1).map(&:strip) : [data.head[0]]
-  end
-  [cols, Rdb::Fast.read_keys(StringIO.new(text), cols.size)]
-end
+      text = $stdin.read.to_s
+      lines = text.lines.map { |l| l.chomp("\n") }
+      cols = args
+      if cols.empty?
+        cols = Rdb::Table.headed?(lines) ? lines[0].split("\t", -1).map(&:strip) : [data.head[0]]
+      end
+      [cols, Rdb::Fast.read_keys(StringIO.new(text), cols.size)]
+    end
 
-def each_key(ncols, keys = nil, &block)
-  if keys
-    keys.each(&block)
-  elsif $stdin.tty?
-    $stdin.each_line { |l| yield l.chomp.split("\t", -1).first(ncols) }
-  else
-    Rdb::Fast.read_keys($stdin, ncols).each { |k| yield k }
+    def each_key(ncols, keys = nil, &block)
+      if keys
+        keys.each(&block)
+      elsif $stdin.tty?
+        $stdin.each_line { |l| yield l.chomp.split("\t", -1).first(ncols) }
+      else
+        Rdb::Fast.read_keys($stdin, ncols).each { |k| yield k }
+      end
+    end
   end
 end
 
@@ -76,7 +79,7 @@ Rdb.register('search', 'Search a table',
   data = Rdb::Fast::Data.new(table)
   need_index(table, o[:m])
   keycols, keys = key_columns(args, data)
-  puts data.head.join("\t"), Rdb::Table.dash_row(data.head) unless o[:h]
+  $stdout.write Rdb::Table.head_text(data.head) unless o[:h]
   each_key(keycols.size, keys) do |key|
     hits = Rdb::Fast.search(data, o[:m], keycols, key, first: o[:s] || o[:l], partial: o[:x], exact: o[:exact])
     hits.each do |h|
@@ -97,7 +100,7 @@ Rdb.register('seek', 'Return the beginning and ending offset of a row', 'seek [-
     Rdb::Fast.search(data, o[:m], keycols, key, first: true).each do |h|
       puts "#{h.row.from} #{h.row.to} #{h.xfrom} #{h.xto}"
       if o[:o]
-        File.write(o[:o], data.head.join("\t") + "\n" + Rdb::Table.dash_row(data.head) + "\n" + h.row.line + "\n")
+        File.write(o[:o], Rdb::Table.head_text(data.head) + h.row.line + "\n")
       end
     end
   end
@@ -137,7 +140,7 @@ Rdb.register('replace', 'Insert a record into a file at specified location',
 
   text = $stdin.read
   lines = text.lines.map { |l| l.chomp("\n") }
-  lines = lines.drop(2) if lines.size >= 2 && Rdb::Table.dash_line?(lines[1].split("\t", -1))
+  lines = lines.drop(2) if Rdb::Table.headed?(lines)
   die 'replace: no input row' if lines.empty?
 
   keycol = Rdb::Fast::Data.new(table).head[0]
@@ -189,33 +192,41 @@ require 'shellwords'
 
 # ---- locks -------------------------------------------------------------------
 
-# Lock files live in a private per-user directory, not loose in the shared
-# /tmp, so other users can neither forge nor delete them.
-def lock_dir
-  dir = File.join(Dir.tmpdir, "rdb-locks-#{Process.uid}")
-  Dir.mkdir(dir, 0o700) unless File.directory?(dir)
-  st = File.lstat(dir)
-  Rdb.die("#{dir}: not a private directory of yours") if st.symlink? || st.uid != Process.uid || (st.mode & 0o077) != 0
-  dir
-end
+module Rdb
+  module Helpers
+    # Lock files live in a private per-user directory, not loose in the shared
+    # /tmp, so other users can neither forge nor delete them.
+    def lock_dir
+      dir = File.join(Dir.tmpdir, "rdb-locks-#{Process.uid}")
+      begin
+        Dir.mkdir(dir, 0o700)
+      rescue Errno::EEXIST
+        nil # made by someone else, maybe at this very moment; checked below
+      end
+      st = File.lstat(dir)
+      Rdb.die("#{dir}: not a private directory of yours") if st.symlink? || st.uid != Process.uid || (st.mode & 0o077) != 0
+      dir
+    end
 
-def lock_file(name)
-  File.join(lock_dir, "L#{File.basename(name)}.#{Digest::MD5.hexdigest(File.expand_path(name))[0, 8]}")
-end
+    def lock_file(name)
+      File.join(lock_dir, "L#{File.basename(name)}.#{Digest::MD5.hexdigest(File.expand_path(name))[0, 8]}")
+    end
 
-# Read-modify-write of a lock file under an exclusive flock, so two lock or
-# unlock calls cannot interleave.  The block gets the held locks and returns
-# the new list of lines, or nil to leave the file alone.
-def with_lock_file(name)
-  File.open(lock_file(name), File::RDWR | File::CREAT, 0o600) do |f|
-    f.flock(File::LOCK_EX)
-    held = f.read.lines(chomp: true).map { |l| l.split.map(&:to_i) }
-    lines = yield held
-    next unless lines
+    # Read-modify-write of a lock file under an exclusive flock, so two lock or
+    # unlock calls cannot interleave.  The block gets the held locks and returns
+    # the new list of lines, or nil to leave the file alone.
+    def with_lock_file(name)
+      File.open(lock_file(name), File::RDWR | File::CREAT, 0o600) do |f|
+        f.flock(File::LOCK_EX)
+        held = f.read.lines(chomp: true).map { |l| l.split.map(&:to_i) }
+        lines = yield held
+        next unless lines
 
-    f.rewind
-    f.truncate(0)
-    f.write(lines.map { |l| "#{l}\n" }.join)
+        f.rewind
+        f.truncate(0)
+        f.write(lines.map { |l| "#{l}\n" }.join)
+      end
+    end
   end
 end
 
@@ -267,20 +278,24 @@ end
 
 # ---- interactive editing --------------------------------------------------------
 
-def show_record(data_head, cells)
-  data_head.each_with_index { |h, i| puts "#{i + 1}  #{h}\t#{cells[i].to_s.strip}" }
-end
+module Rdb
+  module Helpers
+    def show_record(data_head, cells)
+      data_head.each_with_index { |h, i| puts "#{i + 1}  #{h}\t#{cells[i].to_s.strip}" }
+    end
 
-def edit_cells(head, cells)
-  require 'tempfile'
-  Tempfile.create('rdb-edit') do |f|
-    f.write Rdb::Table.new(head, [cells], list: true).to_s
-    f.flush
-    system(*Shellwords.split(ENV['EDITOR'] || 'vi'), f.path) or Rdb.die("editor #{ENV['EDITOR'] || 'vi'} failed")
-    t = Rdb::Table.parse(File.read(f.path))
-    return nil if t.rows.empty?
+    def edit_cells(head, cells)
+      require 'tempfile'
+      Tempfile.create('rdb-edit') do |f|
+        f.write Rdb::Table.new(head, [cells], list: true).to_s
+        f.flush
+        system(*Shellwords.split(ENV['EDITOR'] || 'vi'), f.path) or Rdb.die("editor #{ENV['EDITOR'] || 'vi'} failed")
+        t = Rdb::Table.parse(File.read(f.path))
+        return nil if t.rows.empty?
 
-    head.map { |h| (j = t.head.index(h)) ? t.rows[0][j] : '' }
+        head.map { |h| (j = t.head.index(h)) ? t.rows[0][j] : '' }
+      end
+    end
   end
 end
 
@@ -443,7 +458,7 @@ end
 Rdb.register('validate', 'Find invalid data', "validate 'pattern { action } ...' < tableorlist") do |args|
   die "usage: validate 'pattern { action } ...' < table" unless args.size == 1
   t = table_in
-  puts t.head.join("\t"), Rdb::Table.dash_row(t.head)
+  $stdout.write Rdb::Table.head_text(t.head)
   prog = "BEGIN{OFS=\"\\t\"} #{to_awk(args[0], t.head)} {print}"
   out, ok = awk_text(prog, t.rows)
   $stdout.write out
@@ -512,27 +527,31 @@ end
 
 # ---- exercising the fast-access methods ---------------------------------------------
 
-def sample_table(path, n = 2000)
-  rows = (1..n).map { |i| [i.to_s, "name#{i * 7919 % n}", "city#{i % 97}"] }
-  File.write(path, Rdb::Table.new(%w[Id Name City], rows).to_s)
-end
+module Rdb
+  module Helpers
+    def sample_table(path, n = 2000)
+      rows = (1..n).map { |i| [i.to_s, "name#{i * 7919 % n}", "city#{i % 97}"] }
+      File.write(path, Rdb::Table.new(%w[Id Name City], rows).to_s)
+    end
 
-def time_methods(n = 2000)
-  Dir.mktmpdir do |dir|
-    path = File.join(dir, 'unixtable')
-    sample_table(path, n)
-    %w[s b h i r].each do |m|
-      t0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-      Rdb::Fast.build(path, m, 'Name') unless m == 's'
-      t1 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-      data = Rdb::Fast::Data.new(path)
-      hits = 0
-      (1..200).each do |i|
-        key = m == 'r' ? i.to_s : "name#{i * 13 % n}"
-        hits += Rdb::Fast.search(data, m, ['Name'], key).size
+    def time_methods(n = 2000)
+      Dir.mktmpdir do |dir|
+        path = File.join(dir, 'unixtable')
+        sample_table(path, n)
+        %w[s b h i r].each do |m|
+          t0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+          Rdb::Fast.build(path, m, 'Name') unless m == 's'
+          t1 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+          data = Rdb::Fast::Data.new(path)
+          hits = 0
+          (1..200).each do |i|
+            key = m == 'r' ? i.to_s : "name#{i * 13 % n}"
+            hits += Rdb::Fast.search(data, m, ['Name'], key).size
+          end
+          t2 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+          yield m, t1 - t0, t2 - t1, hits
+        end
       end
-      t2 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-      yield m, t1 - t0, t2 - t1, hits
     end
   end
 end
diff --git a/lib/rdb/cmd/act.rb b/lib/rdb/cmd/act.rb
index dc47633..79245d4 100644
--- a/lib/rdb/cmd/act.rb
+++ b/lib/rdb/cmd/act.rb
@@ -5,43 +5,42 @@
 # an accounting package: each command reads and writes plain /rdb tables in
 # the current directory.
 
-ACT_COMMANDS = %w[act adjust balance bom calcpay calculate cashflow chartdup close consolidate cstate explode
+Rdb::ACT_COMMANDS = %w[act adjust balance bom calcpay calculate cashflow chartdup close consolidate cstate explode
                   fillform foot getjournal invoice sale tax update.inv w2].freeze
 
-# Amounts are decimal numbers, not floats: sums of cents stay exact.
-def num(str)
-  s = str.to_s.strip
-  s.match?(Rdb::NUM) ? BigDecimal(s.sub(/\.\z/, '')) : BigDecimal(s.to_f.to_s)
-end
+module Rdb
+  module Helpers
+    # Amounts are exact decimals (Rational), not floats: sums of cents stay exact.
+    def num(str)
+      Rdb.decimal(str)
+    end
 
-# Two decimals, always (money drops them from whole amounts).
-def fixed2(val)
-  val = BigDecimal(val.to_s) unless val.is_a?(BigDecimal)
-  val.round(2, :half_up).to_s('F').then { |t| t.sub(/\.(\d*)\z/) { ".#{Regexp.last_match(1).ljust(2, '0')}" } }
-end
+    # Two decimals, always (money drops them from whole amounts).
+    def fixed2(val)
+      Rdb.fixed(val, 2)
+    end
 
-def money(val)
-  val = BigDecimal(val.to_s) unless val.is_a?(BigDecimal)
-  return val.to_i.to_s if val == val.to_i
+    def money(val)
+      val == val.to_i ? val.to_i.to_s : Rdb.fixed(val, 2)
+    end
 
-  val.round(2, :half_up).to_s('F').sub(/\.(\d)\z/, '.\10')
-end
+    def need(file)
+      File.exist?(file) || Rdb.die("#{file}: no such table (the /act commands work on tables in the current directory)")
+      Rdb::Table.open(file)
+    end
 
-def need(file)
-  File.exist?(file) || Rdb.die("#{file}: no such table (the /act commands work on tables in the current directory)")
-  Rdb::Table.open(file)
-end
+    def next_date
+      ENV['NEXTDATE'] || Date.today.strftime('%y%m%d')
+    end
 
-def next_date
-  ENV['NEXTDATE'] || Date.today.strftime('%y%m%d')
-end
-
-def account_key(acct)
-  [acct.to_f, acct]
+    def account_key(acct)
+      [acct.to_f, acct]
+    end
+  end
 end
 
 Rdb.register('act', 'List all /act commands', 'act') do |_args|
-  names = ACT_COMMANDS.sort
+  names = Rdb::ACT_COMMANDS.sort
   w = names.map(&:size).max + 2
   names.each_slice(5) { |row| puts row.map { |n| n.ljust(w) }.join.rstrip }
 end
@@ -66,7 +65,7 @@ Rdb.register('foot', 'Foot or subtotal Debits and Credit of ledger', 'foot') do
   out = []
   t.rows.sort_by { |r| account_key(r[0]) }.group_by { |r| r[0] }.each_value do |rows|
     out.concat(rows)
-    out << t.head.map { |h| '-' * [h.size, 1].max }
+    out << Rdb::Table.dash_cells(t.head)
     sub = [''] * t.head.size
     sub[0] = rows.first[0]
     sub[d] = money(rows.sum { |r| num(r[d]) })
@@ -84,7 +83,7 @@ Rdb.register('adjust', 'Create adjusted trial balance table', 'adjust') do |_arg
     m = (meta[h['Account']] ||= {})
     h.each { |k, v| m[k] = v if !v.to_s.strip.empty? && !%w[Debit Credit].include?(k) && !m.key?(k) }
   end
-  net = Hash.new(BigDecimal(0))
+  net = Hash.new(0r)
   [tb, ja].each do |t|
     d = t.index_of('Debit')
     c = t.index_of('Credit')
@@ -104,11 +103,15 @@ Rdb.register('adjust', 'Create adjusted trial balance table', 'adjust') do |_arg
   File.write('adjustedtrial', Rdb::Table.new(head, rows).to_s)
 end
 
-def trial_parts(t)
-  h = t.head
-  fmt = h.index('Format')
-  rows = t.rows.map { |r| { acct: r[0], debit: num(r[h.index('Debit')]), credit: num(r[h.index('Credit')]), fmt: r[fmt].to_s, name: r[h.index('Name')].to_s, row: r } }
-  rows
+module Rdb
+  module Helpers
+    def trial_parts(t)
+      h = t.head
+      fmt = h.index('Format')
+      rows = t.rows.map { |r| { acct: r[0], debit: num(r[h.index('Debit')]), credit: num(r[h.index('Credit')]), fmt: r[fmt].to_s, name: r[h.index('Name')].to_s, row: r } }
+      rows
+    end
+  end
 end
 
 Rdb.register('balance', 'Create balance sheet from adjusted trial balance', 'balance') do |_args|
@@ -183,7 +186,7 @@ Rdb.register('fillform', 'Fill a tax from with adjusted trial balance data', 'fi
   lines = need("taxform.#{args[0]}")
   trial = need('adjustedtrial')
   ti = trial.index_of('Taxline')
-  sums = Hash.new(BigDecimal(0))
+  sums = Hash.new(0r)
   trial.rows.each { |r| sums[r[ti]] += (num(r[trial.index_of('Debit')]) - num(r[trial.index_of('Credit')])).abs }
   rows = lines.rows.map { |r| [r[0], money(sums[r[0]]), r[1].to_s] }
   File.write(args[0], Rdb::Table.new(%w[Taxline Amount Description], rows).to_s)
@@ -205,14 +208,14 @@ Rdb.register('tax', 'Compute tax from income and tax table', 'tax income < taxta
   income = num(args[0])
   rows = table_in.rows.map { |r| r.map { |c| num(c) } }.sort_by(&:first)
   row = rows.reverse.find { |r| r[0] <= income }
-  puts format('%7d', row ? (row[1] + (income - row[0]) * row[2] / 100.0).round : 0)
+  puts format('%7d', row ? (row[1] + (income - row[0]) * row[2] / 100).round(half: :up) : 0)
 end
 
 Rdb.register('cashflow', 'Compute balance column of cash table', 'cashflow < cashtable') do |_args|
   t = table_in
   a = t.index_of('Amount')
   b = t.index_of('Balance')
-  bal = BigDecimal(0)
+  bal = 0r
   rows = t.rows.map do |r|
     r = r.dup
     if r[a].strip.empty? && !r[b].strip.empty?
@@ -250,9 +253,9 @@ end
 Rdb.register('bom', 'Produce bill-of-materials from parts list', 'bom') do |_args|
   part = need('part')
   items = need('saleitem')
-  qty = Hash.new(BigDecimal(0))
+  qty = Hash.new(0r)
   items.rows.each { |r| qty[r[items.index_of('Code')]] += num(r[items.index_of('Qty')]) }
-  need_total = Hash.new(BigDecimal(0))
+  need_total = Hash.new(0r)
   part.rows.each do |r|
     code = r[part.index_of('Code')]
     need_total[r[part.index_of('Subpart')]] += qty[code] * num(r[part.index_of('Count')]) if qty.key?(code)
@@ -263,7 +266,7 @@ end
 Rdb.register('explode', 'Produce table of subparts and their count for a part', 'explode Part Amount [ table ]') do |args|
   die 'usage: explode Part Amount [table]' if args.size < 2
   t = need(args[2] || 'parttable')
-  totals = Hash.new(BigDecimal(0))
+  totals = Hash.new(0r)
   queue = [[args[0], num(args[1])]]
   until queue.empty?
     part, amount = queue.shift
@@ -275,20 +278,24 @@ end
 
 # ---- sales ------------------------------------------------------------------------------
 
-def ask(prompt)
-  print prompt
-  $stdout.flush
-  ($stdin.gets || '').strip
-end
+module Rdb
+  module Helpers
+    def ask(prompt)
+      print prompt
+      $stdout.flush
+      ($stdin.gets || '').strip
+    end
 
-def address_block(customers, number)
-  c = customers.rows.find { |r| r[0] == number }
-  return ["Customer Number #{number}"] unless c
+    def address_block(customers, number)
+      c = customers.rows.find { |r| r[0] == number }
+      return ["Customer Number #{number}"] unless c
 
-  h = customers.head.zip(c).to_h
-  ["Mailing Address for Customer Number #{number}",
-   [h['Title'], h['First'], h['Last'], h['Position']].compact.join(' ').strip,
-   h['Company'], h['Street'], [h['City'], h['State'], h['Country']].compact.join(' ')].compact.reject(&:empty?)
+      h = customers.head.zip(c).to_h
+      ["Mailing Address for Customer Number #{number}",
+       [h['Title'], h['First'], h['Last'], h['Position']].compact.join(' ').strip,
+       h['Company'], h['Street'], [h['City'], h['State'], h['Country']].compact.join(' ')].compact.reject(&:empty?)
+    end
+  end
 end
 
 Rdb.register('invoice', 'Print invoice for a sale order', 'invoice') do |_args|
@@ -359,7 +366,7 @@ Rdb.register('sale', 'Enter sale order, and item, update customer', 'sale') do |
     end
     puts address_block(customers, cust)
     n = Rdb::Table.open('salesorder').rows.map { |r| r[0].to_i }.max.to_i + 1
-    gross = BigDecimal(0)
+    gross = 0r
     items = []
     loop do
       code = ask('Code (Return when done): ')
@@ -375,7 +382,7 @@ Rdb.register('sale', 'Enter sale order, and item, update customer', 'sale') do |
     end
     next if items.empty?
 
-    tax = gross * BigDecimal('0.05')
+    tax = gross * Rational('0.05')
     order = [n.to_s, cust, next_date, '0', fixed2(gross), fixed2(tax), fixed2(gross + tax)]
     puts Rdb::Table.new(%w[Number Cust Date Shipped Gross Tax Total], [order]).to_s
     if ask('Is this correct? (y, n) ').downcase.start_with?('y')
diff --git a/lib/rdb/cmd/convert.rb b/lib/rdb/cmd/convert.rb
index 84fda77..9b7b567 100644
--- a/lib/rdb/cmd/convert.rb
+++ b/lib/rdb/cmd/convert.rb
@@ -105,21 +105,25 @@ end
 
 # ---- names that sound alike ----------------------------------------------------
 
-def soundex_code(word)
-  codes = { 'BFPV' => '1', 'CGJKQSXZ' => '2', 'DT' => '3', 'L' => '4', 'MN' => '5', 'R' => '6' }
-  letters = word.upcase.gsub(/[^A-Z]/, '').chars
-  return '' if letters.empty?
+module Rdb
+  module Helpers
+    def soundex_code(word)
+      codes = { 'BFPV' => '1', 'CGJKQSXZ' => '2', 'DT' => '3', 'L' => '4', 'MN' => '5', 'R' => '6' }
+      letters = word.upcase.gsub(/[^A-Z]/, '').chars
+      return '' if letters.empty?
 
-  code = ->(c) { codes.find { |k, _| k.include?(c) }&.last }
-  out = letters[0].dup
-  last = code.(letters[0])
-  letters.drop(1).each do |c|
-    d = code.(c)
-    out << d if d && d != last
-    last = d unless 'HW'.include?(c)
-    break if out.size == 4
+      code = ->(c) { codes.find { |k, _| k.include?(c) }&.last }
+      out = letters[0].dup
+      last = code.(letters[0])
+      letters.drop(1).each do |c|
+        d = code.(c)
+        out << d if d && d != last
+        last = d unless 'HW'.include?(c)
+        break if out.size == 4
+      end
+      out.ljust(4, '0')
+    end
   end
-  out.ljust(4, '0')
 end
 
 Rdb.register('soundex', 'Convert a name into soundex code', 'soundex < file > file.x ; index -mb file.x Soundex') do |_args|
diff --git a/lib/rdb/cmd/relational.rb b/lib/rdb/cmd/relational.rb
index 4730269..5f47fbe 100644
--- a/lib/rdb/cmd/relational.rb
+++ b/lib/rdb/cmd/relational.rb
@@ -189,7 +189,7 @@ end
 # total, mean, maximum, minimum, width, precision and datatype are one program
 # that decides what to compute from the name it was called by.
 
-STATS = {
+Rdb::STATS = {
   'total' => 'Sum a column',
   'mean' => 'Display the mean of a column',
   'maximum' => 'Display the maximum value in a column',
@@ -199,7 +199,7 @@ STATS = {
   'datatype' => 'Display the data type of each column selected'
 }.freeze
 
-STATS.each do |cmd, desc|
+Rdb::STATS.each do |cmd, desc|
   Rdb.register(cmd, desc, "#{cmd} [ -l ] [ column ... ] < table") do |args|
     list = args.first == '-l'
     args.shift if list
@@ -209,7 +209,7 @@ STATS.each do |cmd, desc|
     sel.each do |i|
       vals = t.rows.map { |r| r[i] }
       filled = vals.reject { |v| v.strip.empty? }
-      nums = filled.all? { |v| numeric?(v) } ? vals.map { |v| v.strip.empty? ? BigDecimal(0) : dec_num(v) } : nil
+      nums = filled.all? { |v| numeric?(v) } ? vals.map { |v| dec_num(v) } : nil
       dec = filled.map { |v| decimals(v) }.max.to_i
       result[i] =
         case name
@@ -260,7 +260,7 @@ Rdb.register('subtotal', 'Output subtotals of columns in a table',
     end
     if list
       out.concat(group)
-      out << t.head.map { |h| '-' * [h.size, 1].max }
+      out << Rdb::Table.dash_cells(t.head)
     end
     out << sub
     group = []
diff --git a/lib/rdb/cmd/report.rb b/lib/rdb/cmd/report.rb
index a11f482..e44a8b6 100644
--- a/lib/rdb/cmd/report.rb
+++ b/lib/rdb/cmd/report.rb
@@ -4,19 +4,23 @@
 
 require 'shellwords'
 
-# Fill in a form for one row: <Column> is replaced by the value, <!command!>
-# by the output of the shell command, and <!cmd <Column>!> passes data to it.
-# Values inside a command are shell-escaped, so a cell can never add commands
-# of its own; they arrive as one word each (do not put them in quotes).
-def fill_form(form, head, row)
-  values = head.zip(row).to_h { |h, v| [h.strip, v.to_s] }
-  form.gsub(/<!(.*?)!>|<([^<>!\n]*)>/m) do
-    if Regexp.last_match(1)
-      cmd = Regexp.last_match(1).gsub(/<([^<>!\n]*)>/) { Shellwords.escape(values.fetch(Regexp.last_match(1).strip, Regexp.last_match(0))) }
-      `#{cmd}`
-    else
-      name = Regexp.last_match(2).strip
-      values.key?(name) ? values[name] : Regexp.last_match(0)
+module Rdb
+  module Helpers
+    # Fill in a form for one row: <Column> is replaced by the value, <!command!>
+    # by the output of the shell command, and <!cmd <Column>!> passes data to it.
+    # Values inside a command are shell-escaped, so a cell can never add commands
+    # of its own; they arrive as one word each (do not put them in quotes).
+    def fill_form(form, head, row)
+      values = head.zip(row).to_h { |h, v| [h.strip, v.to_s] }
+      form.gsub(/<!(.*?)!>|<([^<>!\n]*)>/m) do
+        if Regexp.last_match(1)
+          cmd = Regexp.last_match(1).gsub(/<([^<>!\n]*)>/) { Shellwords.escape(values.fetch(Regexp.last_match(1).strip, Regexp.last_match(0))) }
+          `#{cmd}`
+        else
+          name = Regexp.last_match(2).strip
+          values.key?(name) ? values[name] : Regexp.last_match(0)
+        end
+      end
     end
   end
 end
@@ -76,9 +80,13 @@ Rdb.register('screen', 'Convert a form into a screen-input shell program', 'scre
   puts ': append row', %(echo "#{names.map { |x| "$#{x}" }.join("\t")}")
 end
 
-def label_lines(head, row)
-  h = head.zip(row).to_h
-  [h['Name'], h['Company'], h['Street'], "#{h['City']}, #{h['State']} #{h['ZIP']}".strip].compact
+module Rdb
+  module Helpers
+    def label_lines(head, row)
+      h = head.zip(row).to_h
+      [h['Name'], h['Company'], h['Street'], "#{h['City']}, #{h['State']} #{h['ZIP']}".strip].compact
+    end
+  end
 end
 
 Rdb.register('label', 'Print mailing labels from a mailing list', 'label < list') do |_args|
diff --git a/lib/rdb/cmd/term.rb b/lib/rdb/cmd/term.rb
index 0fc0513..680f8e1 100644
--- a/lib/rdb/cmd/term.rb
+++ b/lib/rdb/cmd/term.rb
@@ -4,20 +4,24 @@ require 'shellwords'
 
 # Help, manual pages, terminal helpers, menus and housekeeping.
 
-ESC = "\e"
-TERM_CAPS = {
-  'cl' => "#{ESC}[H#{ESC}[2J", 'ho' => "#{ESC}[H", 'ce' => "#{ESC}[K", 'cd' => "#{ESC}[J",
-  'cm' => "#{ESC}[%i%d;%dH", 'so' => "#{ESC}[7m", 'se' => "#{ESC}[m", 'us' => "#{ESC}[4m",
-  'ue' => "#{ESC}[m", 'mb' => "#{ESC}[5m", 'md' => "#{ESC}[1m", 'me' => "#{ESC}[m",
-  'as' => "#{ESC}(0", 'ae' => "#{ESC}(B", 'up' => "#{ESC}[A", 'do' => "#{ESC}[B", 'bs' => "\b"
+Rdb::ESC = "\e"
+Rdb::TERM_CAPS = {
+  'cl' => "#{Rdb::ESC}[H#{Rdb::ESC}[2J", 'ho' => "#{Rdb::ESC}[H", 'ce' => "#{Rdb::ESC}[K", 'cd' => "#{Rdb::ESC}[J",
+  'cm' => "#{Rdb::ESC}[%i%d;%dH", 'so' => "#{Rdb::ESC}[7m", 'se' => "#{Rdb::ESC}[m", 'us' => "#{Rdb::ESC}[4m",
+  'ue' => "#{Rdb::ESC}[m", 'mb' => "#{Rdb::ESC}[5m", 'md' => "#{Rdb::ESC}[1m", 'me' => "#{Rdb::ESC}[m",
+  'as' => "#{Rdb::ESC}(0", 'ae' => "#{Rdb::ESC}(B", 'up' => "#{Rdb::ESC}[A", 'do' => "#{Rdb::ESC}[B", 'bs' => "\b"
 }.freeze
 
-def command_rows
-  Rdb::COMMANDS.values.reject { |c| c.name.include?('.list') || c.name == 'rdb.install' }.sort_by(&:name)
-end
+module Rdb
+  module Helpers
+    def command_rows
+      Rdb::COMMANDS.values.reject { |c| c.name.include?('.list') || c.name == 'rdb.install' }.sort_by(&:name)
+    end
 
-def syntax_of(cmd)
-  cmd.syntax.sub(/\A\S+\s*/, '')
+    def syntax_of(cmd)
+      cmd.syntax.sub(/\A\S+\s*/, '')
+    end
+  end
 end
 
 Rdb.register('rdb.list', 'List all /rdb programs', 'rdb') do |_args|
@@ -80,56 +84,60 @@ end
 
 # ---- manual pages ---------------------------------------------------------------
 
-def troff_clean(str)
-  # a literal backslash (\\ or \e) is parked in \0 so that later rules cannot see it
-  str.gsub('\\\\', "\0").gsub(/\\f[BIRP]/, '').gsub('\\e', "\0").gsub('\\(em', ' -- ').gsub('\\(aa', "'")
-     .gsub('\\-', '-').gsub('\\&', '').gsub('\\*(UX', 'UNIX').gsub('``', '"').gsub("''", '"').gsub('\\ ', ' ')
-     .gsub(/\\\(..|\\\*\(..|\\[a-z]/, '').gsub("\0", '\\')
-end
+module Rdb
+  module Helpers
+    def troff_clean(str)
+      # a literal backslash (\\ or \e) is parked in \0 so that later rules cannot see it
+      str.gsub('\\\\', "\0").gsub(/\\f[BIRP]/, '').gsub('\\e', "\0").gsub('\\(em', ' -- ').gsub('\\(aa', "'")
+         .gsub('\\-', '-').gsub('\\&', '').gsub('\\*(UX', 'UNIX').gsub('``', '"').gsub("''", '"').gsub('\\ ', ' ')
+         .gsub(/\\\(..|\\\*\(..|\\[a-z]/, '').gsub("\0", '\\')
+    end
 
-def render_man(src)
-  out = []
-  para = []
-  verbatim = false
-  flush = lambda do
-    unless para.empty?
-      words = para.join(' ').split
-      line = ''
-      words.each { |w| line.size + w.size + 1 > 72 ? (out << line; line = w) : line = (line.empty? ? w : "#{line} #{w}") }
-      out << line unless line.empty?
-      para.clear
-    end
-  end
-  src.each_line do |raw|
-    l = raw.chomp
-    if l.start_with?('.')
-      macro, rest = l[1..].split(/\s+/, 2)
-      rest = rest.to_s.strip.delete_prefix('"').delete_suffix('"')
-      case macro
-      when 'TH', 'II', 'ta', 'ne', 'R', 'RE', 'SO', 'B1', 'B2', 'nf', 'fi', 'br' then nil
-      when '\\"' then nil
-      when 'PC' then flush.(); out << ''
-      when 'SH' then flush.(); out << '' << troff_clean(rest).upcase
-      when 'PP', 'sp' then flush.(); out << ''
-      when 'DM', 'DS' then flush.(); verbatim = true
-      when 'DE' then verbatim = false
-      when 'IP' then flush.(); out << ''; para << troff_clean(rest.split(/\s+\d/).first.to_s)
-      when 'B', 'I', 'BR', 'IR', 'RB', 'RI' then para << troff_clean(rest.delete('"')).gsub(/\s+/, ' ') unless verbatim
-      else nil
+    def render_man(src)
+      out = []
+      para = []
+      verbatim = false
+      flush = lambda do
+        unless para.empty?
+          words = para.join(' ').split
+          line = ''
+          words.each { |w| line.size + w.size + 1 > 72 ? (out << line; line = w) : line = (line.empty? ? w : "#{line} #{w}") }
+          out << line unless line.empty?
+          para.clear
+        end
+      end
+      src.each_line do |raw|
+        l = raw.chomp
+        if l.start_with?('.')
+          macro, rest = l[1..].split(/\s+/, 2)
+          rest = rest.to_s.strip.delete_prefix('"').delete_suffix('"')
+          case macro
+          when 'TH', 'II', 'ta', 'ne', 'R', 'RE', 'SO', 'B1', 'B2', 'nf', 'fi', 'br' then nil
+          when '\\"' then nil
+          when 'PC' then flush.(); out << ''
+          when 'SH' then flush.(); out << '' << troff_clean(rest).upcase
+          when 'PP', 'sp' then flush.(); out << ''
+          when 'DM', 'DS' then flush.(); verbatim = true
+          when 'DE' then verbatim = false
+          when 'IP' then flush.(); out << ''; para << troff_clean(rest.split(/\s+\d/).first.to_s)
+          when 'B', 'I', 'BR', 'IR', 'RB', 'RI' then para << troff_clean(rest.delete('"')).gsub(/\s+/, ' ') unless verbatim
+          else nil
+          end
+        elsif verbatim
+          out << "    #{troff_clean(l)}"
+        elsif l.start_with?("\t", ' ')
+          flush.()
+          out << "    #{troff_clean(l.strip)}"
+        elsif l.strip.empty?
+          flush.()
+        else
+          para << troff_clean(l.strip)
+        end
       end
-    elsif verbatim
-      out << "    #{troff_clean(l)}"
-    elsif l.start_with?("\t", ' ')
       flush.()
-      out << "    #{troff_clean(l.strip)}"
-    elsif l.strip.empty?
-      flush.()
-    else
-      para << troff_clean(l.strip)
+      out.join("\n").squeeze("\n")
     end
   end
-  flush.()
-  out.join("\n").squeeze("\n")
 end
 
 Rdb.register('man', 'Display the manual page for a command', 'man [-g] command') do |args|
@@ -161,21 +169,21 @@ end
 
 Rdb.register('termput', 'Get terminal capability from /etc/termcap file', 'termput capability') do |args|
   die 'usage: termput capability' unless args.size == 1
-  $stdout.print TERM_CAPS.fetch(args[0]) { die "no such capability '#{args[0]}'" }
+  $stdout.print Rdb::TERM_CAPS.fetch(args[0]) { die "no such capability '#{args[0]}'" }
 end
 
 Rdb.register('tset', 'Fetch termcap entry for a terminal type', 'tset [ TERM ]') do |args|
   term = args.first || ENV['TERM'] || 'ansi'
-  puts ":#{TERM_CAPS.map { |k, v| "#{k}=#{v.inspect[1..-2]}" }.join(':')}:co##{ENV['COLUMNS'] || 80}:li##{ENV['LINES'] || 24}:tc=#{term}:"
+  puts ":#{Rdb::TERM_CAPS.map { |k, v| "#{k}=#{v.inspect[1..-2]}" }.join(':')}:co##{ENV['COLUMNS'] || 80}:li##{ENV['LINES'] || 24}:tc=#{term}:"
 end
 
 Rdb.register('clear.rdb', "Clear the terminal's screen", 'clear.rdb') do |_args|
-  $stdout.print TERM_CAPS['cl']
+  $stdout.print Rdb::TERM_CAPS['cl']
 end
 
 Rdb.register('cursor', 'Move the cursor to the row and column requested', 'cursor row col [ CURSOR ]') do |args|
   die 'usage: cursor row col [CURSOR]' if args.size < 2
-  $stdout.print "#{ESC}[#{args[0].to_i};#{args[1].to_i}H"
+  $stdout.print "#{Rdb::ESC}[#{args[0].to_i};#{args[1].to_i}H"
   $stdout.flush
 end
 
diff --git a/lib/rdb/cmd/text.rb b/lib/rdb/cmd/text.rb
index b28e037..ee6303e 100644
--- a/lib/rdb/cmd/text.rb
+++ b/lib/rdb/cmd/text.rb
@@ -2,16 +2,20 @@
 
 # Formatting tables and working with text.
 
-def justify_numbers(cells)
-  parts = cells.map { |c| c.empty? ? ['', nil] : c.split('.', 2) }
-  int_w = parts.map { |i, _| i.size }.max
-  frac_w = parts.map { |_, f| f ? f.size : 0 }.max
-  cells.zip(parts).map do |c, (i, f)|
-    next ' ' * (int_w + (frac_w.zero? ? 0 : frac_w + 1)) if c.empty?
+module Rdb
+  module Helpers
+    def justify_numbers(cells)
+      parts = cells.map { |c| c.empty? ? ['', nil] : c.split('.', 2) }
+      int_w = parts.map { |i, _| i.size }.max
+      frac_w = parts.map { |_, f| f ? f.size : 0 }.max
+      cells.zip(parts).map do |c, (i, f)|
+        next ' ' * (int_w + (frac_w.zero? ? 0 : frac_w + 1)) if c.empty?
 
-    s = i.rjust(int_w)
-    s += f ? ".#{f.ljust(frac_w)}" : ' ' * (frac_w.zero? ? 0 : frac_w + 1)
-    s
+        s = i.rjust(int_w)
+        s += f ? ".#{f.ljust(frac_w)}" : ' ' * (frac_w.zero? ? 0 : frac_w + 1)
+        s
+      end
+    end
   end
 end
 
@@ -112,7 +116,7 @@ Rdb.register('pad', 'Add extra spaces at end of last column', 'pad [-number] < t
   if t.list
     t.with(rows: t.rows.map { |r| r[0...-1] + [r.last + ' ' * n] }).write
   else
-    $stdout.write t.head.join("\t"), "\n", Rdb::Table.dash_row(t.head), "\n"
+    $stdout.write Rdb::Table.head_text(t.head)
     t.rows.each { |r| puts (r[0...-1] + [r.last + ' ' * n]).join("\t") }
   end
 end
diff --git a/lib/rdb/env.rb b/lib/rdb/env.rb
index bfce2ff..701c6d7 100644
--- a/lib/rdb/env.rb
+++ b/lib/rdb/env.rb
@@ -1,8 +1,13 @@
 # frozen_string_literal: true
 
 module Rdb
+  # Helpers of single command files (lib/rdb/cmd/*.rb) go in here, not on
+  # Object; every Env includes them.
+  module Helpers; end
+
   # Command blocks run inside an Env, which holds the helpers they share.
   class Env
+    include Helpers
     attr_reader :name
 
     def initialize(name)
@@ -30,14 +35,12 @@ module Rdb
       str.strip[/\.(\d+)\z/, 1].to_s.size
     end
 
-    # Decimal arithmetic, so that 0.1 + 0.2 is 0.3 and money adds up to the cent.
     def dec_num(str)
-      BigDecimal(str.strip.sub(/\.\z/, ''))
+      Rdb.decimal(str)
     end
 
     def fmt(num, dec)
-      num = BigDecimal(num.to_s) unless num.is_a?(BigDecimal)
-      dec.zero? ? num.round(0, :half_up).to_i.to_s : num.round(dec, :half_up).to_s('F').then { |t| t.sub(/\.(\d*)\z/) { ".#{Regexp.last_match(1).ljust(dec, '0')}" } }
+      Rdb.fixed(num, dec)
     end
 
     def blank_row?(row)
@@ -102,18 +105,14 @@ module Rdb
 
     # Run an awk program over rows (tab separated) and return the output rows.
     def awk(prog, rows)
-      input = rows.map { |r| r.join("\t") }.join("\n")
-      input += "\n" unless input.empty?
-      out, err, st = Open3.capture3('awk', '-F', "\t", prog, stdin_data: input)
-      $stderr.print err unless err.empty?
-      exit 1 unless st.success?
+      out, ok = awk_text(prog, rows)
+      exit 1 unless ok
       out.each_line.map { |l| l.chomp.split("\t", -1) }
     end
 
     # Raw output of awk, for programs that print their own text.
     def awk_text(prog, rows)
-      input = rows.map { |r| r.join("\t") }.join("\n")
-      input += "\n" unless input.empty?
+      input = rows.map { |r| "#{r.join("\t")}\n" }.join
       out, err, st = Open3.capture3('awk', '-F', "\t", prog, stdin_data: input)
       $stderr.print err unless err.empty?
       [out, st.success?]
diff --git a/lib/rdb/fast.rb b/lib/rdb/fast.rb
index 15eba93..0c0dc56 100644
--- a/lib/rdb/fast.rb
+++ b/lib/rdb/fast.rb
@@ -129,7 +129,7 @@ module Rdb
       when 'b'
         k = data.column(keycol)
         body = live_rows(data).sort_by { |r| r.cells[k].to_s.strip }.map { |r| r.line + "\n" }
-        Rdb.write_file(path, data.head.join("\t") + "\n" + Table.dash_row(data.head) + "\n" + body.join)
+        Rdb.write_file(path, Table.head_text(data.head) + body.join)
       end
     end
 
@@ -393,7 +393,7 @@ module Rdb
       return [] if text.empty?
 
       lines = text.lines.map { |l| l.chomp("\n") }
-      if lines.size >= 2 && Table.dash_line?(lines[1].split("\t", -1))
+      if Table.headed?(lines)
         lines.drop(2).reject(&:empty?).map { |l| l.split("\t", -1).first(ncols) }
       else
         lines.reject(&:empty?).map { |l| l.split("\t", -1).first(ncols) }
diff --git a/lib/rdb/table.rb b/lib/rdb/table.rb
index 744dbce..65693cd 100644
--- a/lib/rdb/table.rb
+++ b/lib/rdb/table.rb
@@ -28,6 +28,11 @@ module Rdb
       end
     end
 
+    # Do these lines (chomped) start with a head line and a dash line?
+    def self.headed?(lines)
+      lines.size >= 2 && dash_line?(lines[1].split("\t", -1))
+    end
+
     def self.parse(text)
       text = utf8(text)
       return parse_list(text) if text.start_with?("\n")
@@ -78,15 +83,22 @@ module Rdb
     def to_s
       return list_text if @list
 
-      out = +''
-      out << @head.join("\t") << "\n"
-      out << Table.dash_row(@head) << "\n"
+      out = Table.head_text(@head)
       @rows.each { |r| out << r.join("\t") << "\n" }
       out
     end
 
+    def self.dash_cells(head)
+      head.map { |h| '-' * [h.size, 1].max }
+    end
+
     def self.dash_row(head)
-      head.map { |h| '-' * [h.size, 1].max }.join("\t")
+      dash_cells(head).join("\t")
+    end
+
+    # Head line and dash line, each with its newline.
+    def self.head_text(head)
+      +"#{head.join("\t")}\n#{dash_row(head)}\n"
     end
 
     def list_text
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 73fb758..6a4ca25 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -12,6 +12,10 @@ DEMO = File.join(ROOT, 'demo')
 # Each test runs in a scratch copy of demo/, so commands that change files
 # (append, delete, replace ...) never touch the originals.
 class RdbCase < Minitest::Test
+  # Tests spawn their own processes in their own directory, so they can run
+  # side by side (N=1 in MT_CPU runs them one at a time).
+  parallelize_me!
+
   def setup
     @dir = Dir.mktmpdir('rdb-test')
     FileUtils.cp_r(Dir[File.join(DEMO, '*')], @dir)