# Utility to run given Perl program line by line and print out
# values as comments (for annotation)
# Strictly brute-force. Watch out for side-effects!
# 
# Vim users can use this like:
# vmap <F9> !perl annotate.pl<CR>
# nmap <F9> :.!perl annotate.pl<CR>

use strict;

package Annotate;    # keep my own namespace so as not to pollute main
use Data::Dumper();
$Data::Dumper::Indent = 0;
$Data::Dumper::Terse  = 1;
$Data::Dumper::Useqq  = 1;

# these are locals so they're not visible in the evals.
use vars qw(@program @sresults @aresults $programText $i $sresult @are
+sult);

while (<>)
{
    s/[\n\r\s]+$//;
    s/\s*##=> (?:array|scalar).*//;
    push ( @program, $_ );
}

# set up Perl defaults:
$programText = "no strict; package main;";

for $i ( 0 .. $#program )
{
    $programText .= $program[$i] . "\n";
    $sresult = eval $programText;
    next if $@;
    @aresult = eval $programText;

    if ( @aresult == 1 && $aresult[0] == $sresult )
    {
        $sresults[$i] = $sresult;
    }
    elsif ( scalar(@aresult) == $sresult )
    {
        $aresults[$i] = [@aresult];
    }
    else    # different scalar and array results
    {
        $sresults[$i] = $sresult;
        $aresults[$i] = [@aresult];
    }
}

die "error: $@" if $@;

sub result { Data::Dumper->Dump( [shift] ) }

for $i ( 0 .. $#program )
{
    print $program[$i];
    if ( $program[$i] =~ /^[^#]*;(\s*#.*)?$/
      && ( defined( $sresults[$i] ) || defined( $aresults[$i] ) ) )
    {
        print "\t##=>";
        print " scalar: ", result( $sresults[$i] ) if defined( $sresul
+ts[$i] );
        print " array: ",  result( $aresults[$i] ) if defined( $aresul
+ts[$i] );
    }
    print "\n";
}

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In reply to Annotate Perl code with return values by bikeNomad

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