NAME
    BATsh - Bilingual Shell for cmd.exe and bash in one script
    (self-contained)

VERSION
    Version 0.02

SYNOPSIS
      use BATsh;

      # Run a bilingual .batsh script
      BATsh->run('myscript.batsh');
      BATsh->run('myscript.batsh', args => ['arg1', 'arg2']);

      # Run source inline
      BATsh->run_string('echo hello from sh');
      BATsh->run_string("SET MSG=hello\nECHO %MSG%");

      # Interactive REPL
      BATsh->repl();

      # CMD features: pipe, tilde modifiers, SET /P
      BATsh->run_string('ECHO hello | perl -e "while(<STDIN>){chomp;print uc(\$_).chr(10)}"');
      BATsh->run_string("SET /P NAME=Enter name: ");

      # SH features: functions, expansions, pipelines, redirection
      BATsh->run_string(<<'BATSH');
      greet() {
          echo "Hello, \$1"
      }
      greet world
      x=\$(echo hello | perl -e 'while(<STDIN>){chomp;print uc}')
      echo \$x
      echo out > /tmp/out.txt
      BATSH

      # Perl 5.005_03 and later; pure-Perl, no external shell required.

DESCRIPTION
  Executive Summary
    BATsh is a self-contained bilingual shell interpreter written in pure
    Perl. It runs cmd.exe batch syntax and bash/sh syntax in the same script
    file, switching automatically between CMD mode and SH mode on a
    line-by-line basis. No external cmd.exe, bash, or sh is required --
    everything runs inside Perl.

  Mixed-Mode Sample
    The following script demonstrates cmd.exe and bash sections coexisting
    and sharing variables through the common BATsh::Env variable store.

      :: -- CMD section: sets a variable and calls a SH function via bridge --
      @ECHO OFF
      SET LANG=BATsh
      SET COUNT=3

      # -- SH section: reads CMD variables, uses functions and pipeline --
      greet() {
          echo "Hello from $1 (bash/sh mode)"
      }
      greet $LANG
      for i in 1 2 3; do echo "  item $i of $COUNT"; done
      result=$(echo "$LANG" | perl -e 'while(<STDIN>){chomp;print uc}')
      echo "Uppercase: $result"
      echo "log line" >> /tmp/batsh_demo.txt

      :: -- CMD section again: reads variable set by SH side --
      ECHO Back in CMD mode
      ECHO Uppercase result: %result%

    BATsh features (both modes): pipelines (|), I/O redirection (> >> <
    2>&1), variable expansion (${var%pat} ${var^^} ${#var}), functions,
    shift, local.

FULL DESCRIPTION
    BATsh is a self-contained bilingual shell interpreter written in pure
    Perl. It implements both the cmd.exe command set and the sh/bash command
    set entirely in Perl -- no external cmd.exe, bash, or sh is required.

    Scripts are divided into CMD sections (uppercase first token) and SH
    sections (lowercase first token). Both sections share a common variable
    store via BATsh::Env, so variables set in a CMD section are immediately
    visible in the next SH section and vice versa.

CMD MODE
    Any line whose first token is all uppercase (A-Z, 0-9, path chars) is a
    CMD line. CMD sections are executed by BATsh::CMD, which implements:

      ECHO, @ECHO OFF/ON
      SET VAR=value, SET /A expr (arithmetic)
      SET /P VAR=Prompt  (interactive prompt input from STDIN)
      IF "A"=="B" ... ELSE ..., IF /I (case-insensitive), IF NOT
      IF EXIST "path with spaces", IF DEFINED var, IF ERRORLEVEL n
      FOR %%V IN (list) DO ..., FOR /L %%V IN (s,step,e) DO ...
      FOR /F "tokens= delims= skip= eol= usebackq" %%V IN (src) DO ...
      GOTO :label, :label, GOTO :EOF
      CALL :label [args], CALL file.batsh
      SHIFT, SHIFT /N
      SETLOCAL [ENABLEDELAYEDEXPANSION|DISABLEDELAYEDEXPANSION], ENDLOCAL
      CD, DIR, COPY, DEL, MOVE, MKDIR, RMDIR, REN, TYPE
      PAUSE, EXIT [/B] [code], CLS, TITLE, VER, PUSHD, POPD
      cmd1 | cmd2  (pipeline via temporary file)
      &, &&, ||  (sequential, conditional-and, conditional-or)

  Variable Expansion
    "%VAR%" references are expanded before each line is dispatched. Variable
    names are case-insensitive ("SET foo=x" is visible as "%FOO%").

    Inside parenthesised IF and FOR blocks, "%VAR%" is expanded at parse
    time (before any commands in the block run), matching cmd.exe behaviour.
    To see a value updated inside a block, use delayed expansion:

      SETLOCAL ENABLEDELAYEDEXPANSION
      SET X=old
      IF 1==1 (
          SET X=new
          ECHO !X!       &:: prints "new" (delayed)
          ECHO %X%       &:: prints "old" (parse-time)
      )
      ENDLOCAL

  Batch Parameters
    %0 is the script path (absolute); %1..%9 are positional arguments; "%*"
    is all arguments joined by space. "SHIFT" / "SHIFT /N" shifts the
    positional parameters. "CALL :label" saves and restores caller's
    arguments.

    Batch-parameter tilde modifiers expand %0..%9 components:

      %~0    dequote (strip surrounding "...")
      %~f1   full absolute path of %1
      %~d1   drive letter only   (e.g. C:)
      %~p1   directory path only (with trailing /)
      %~n1   filename without extension
      %~x1   extension only       (e.g. .bat)
      %~dp0  drive + directory    (most common usage)
      %~nx1  filename + extension

  Redirection and Compound Commands
      ECHO text > file      stdout overwrite
      ECHO text >> file     stdout append
      prog 2> err.txt       stderr redirect
      & cmd                 sequential execution
      cmd1 && cmd2          run cmd2 only if cmd1 succeeded (ERRORLEVEL 0)
      cmd1 || cmd2          run cmd2 only if cmd1 failed   (ERRORLEVEL != 0)

    The "^" character escapes the next character:

      ECHO a^&b    prints  a&b   (& not treated as compound separator)
      ECHO a^^b    prints  a^b
      ECHO text^   next line is joined (line continuation)

SH MODE
    Any line whose first token contains a lowercase letter is a SH line. SH
    sections are executed by BATsh::SH, which implements:

      VAR=value, export VAR=value, unset VAR
      echo, printf
      if/then/elif/else/fi
      for VAR in list; do ... done
      while condition; do ... done
      until condition; do ... done
      case $var in pattern) ... ;; esac
      test / [ ... ]  (file, string, and integer comparisons)
      cd, pwd, exit, true, false, :, read, shift [N], local VAR=value
      $(( arithmetic )) -- +, -, *, /, %, and $1..$9 inside
      $( command ) and `command`  (command substitution, nested)
      cmd1 | cmd2 [| cmd3 ...]  (pipeline via temporary file)
      cmd1 && cmd2, cmd1 || cmd2, cmd1 ; cmd2  (compound commands)
      > >> < 2> 2>> 2>&1 1>&2  (I/O redirection)
      name() { ... }, function name { ... }  (function definitions)
      $VAR, ${VAR}, $1..$9, $@, $*, $#, $?, $$, $0
      ${VAR:-default}, ${VAR:=default}, ${VAR:+alt}
      ${VAR%pat}, ${VAR%%pat}   -- shortest/longest suffix removal
      ${VAR#pat}, ${VAR##pat}   -- shortest/longest prefix removal
      ${VAR/pat/rep}, ${VAR//pat/rep}  -- first/all substitution
      ${VAR^^}, ${VAR^}, ${VAR,,}, ${VAR,}  -- case conversion
      ${VAR:N:L}, ${VAR:N}  -- substring
      ${#VAR}  -- string length
      source / . file

REQUIREMENTS
    Perl 5.005_03 or later. Core modules only. No external shell required.

BUGS AND LIMITATIONS
    The built-in CMD interpreter does not support:

    *   "FOR /F" with "usebackq" backtick-quoted commands on Windows (the
        "cmd /c" subprocess path is untested on Windows)

    *   "CHOICE", "TIMEOUT", "XCOPY", "ROBOCOPY", "FINDSTR", "SORT", "MORE"
        and other external utilities (delegated to the OS)

    The built-in SH interpreter does not support:

    *   Background execution ("&" at end of command)

    *   Here-documents ("<<")

    *   Process substitution ("<(cmd)")

    Pipeline ("|"), I/O redirection (">" ">>" "<" "2>" "2>>" "2>&1"),
    compound commands ("&&" "||" ";"), and function definitions are all
    supported.

    Section boundary detection is token-based (uppercase vs. lowercase first
    token). Mixed-case first tokens are treated as SH.

    Please report bugs via the issue tracker:
    <https://github.com/ina-cpan/BATsh/issues>

SEE ALSO
    BATsh::CMD, BATsh::SH, BATsh::Env

AUTHOR
    INABA Hitoshi <ina@cpan.org>

LICENSE
    This software is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

