Dear Monks,

I'm in the middle of updating a module that grades Excel spreadsheets by comparing the contents of cells to a model text file parsed by Parse::RecDescent. Strings are allowed in the comparisons, but in the previous version of the module, they were hacked in by simply returning a manually unescaped version of the matched text, e.g.:

quoted_string: '"' m{(([\\]"|[^"])*)} '"' 
{
  $item[2] =~ s{\\"}{"}g;   # Unescape quotes
  $item[2] =~ s{\\\\}{\\}g; # Unescape backslashes
  $item[2];
}

[download]

I want to use the <perl_quotelike> production (a wrapper around Text::Balanced), for greater flexibility with quoted strings and regexes. The problem is that <perl_quotelike> extracts the Perl-ish string/regex, but the only way I can think of to interpret the string/regex correctly (which could contain quotes, backslashes, Unicode hexes, regex modifers, etc.) is to eval the relevant bits, e.g.:

quoted_string: <perl_quotelike>
{
  my ( $name, $ldelim, $text, $rdelim ) = @{ $item[1] };
  if ( $name eq 'qq' ) {
    $text = eval 'qq' . $ldelim . $text . $rdelim;
  }
  # etc...
}

[download]

Which is nasty, as the model file text could then contain:

A1  mean(B1:B10)           &&
A2  "Something innocuous"  &&
A3  C1/C2                  &&
A4  qq(Oh dear @{[ system 'rm -rf *' ]})

[download]

Am I missing something, or am I trapped between either implementing my own interpolator/unescaper (which certainly won't be able to replicate all the useful features of perl quoting and regex modifiers), or using string eval (and hoping that no-one does anything nasty)?

In reply to Using Parse::RecDescent to parse Perl-ish strings without resorting to string eval by polypompholyx

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