Interesting this ideone if it really lets you run actual perl code, anyway, its best in the future if you also post the code here in code tags, here is the output on my machine 

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my $input = $ARGV[0] // "2 * 3 + 4 # and a comment\n";

my @tokens;

$^R and push @tokens, [$^R, $1] while $^R = undef,
  $input =~ /( \#.*$
  | \s+
  | [+-] (?{'AddOp'})
  | [*\/] (?{'MulOp'})
  | \d+ (?{'Number'})
  | \( (?{'OpenParen'})
  | \) (?{'CloseParen'})
  | . (?{ die "Syntax error at position $-[0]\n" })
  )/gmx;

print Dumper \@tokens;
$ perl sUnahm
$VAR1 = [
          [
            'Number',
            '2'
          ],
          [
            'MulOp',
            '*'
          ],
          [
            'Number',
            '3'
          ],
          [
            'AddOp',
            '+'
          ],
          [
            'Number',
            '4'
          ]
        ];

[download]

In reply to Re^2: RFC: Parsing with perl - Regexes and beyond by beech
in thread RFC: Parsing with perl - Regexes and beyond by moritz

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