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This is something I made up for a quick tester of regexes against strings; since it remembers both, either one can be 'adjusted' as necessary. It shows not only whether the match succeeds but also anything that was captured by the memory parens. It works with stand-alone regexes, substitution expressions, and the 'tr' operator. It's not perfect - it's probably somewhat fragile - but it's worked well for me for several months now, happily parsing my regexes by the dozen. I hope others find it useful.

#!/usr/bin/perl -w
# Created by Ben Okopnik on Mon Mar 24 23:35:26 EDT 2008
# Regex Explorer

use strict qw/vars/;
use Term::ReadLine;
my $term = new Term::ReadLine 'Regex Explorer';
my $OUT = $term -> OUT || \*STDOUT;

print $OUT "Exit by entering an empty string at any prompt.\n\n";

{
    my $string = $term->readline("String: ");
    exit if $string =~ /^$/i;
    my $regex = $term->readline("Regex: ");
    exit if $regex =~ /^$/i;
    if ($regex !~ /^\s*((?:y|tr|s|m)\W|\/)/){
        print $OUT "The regex must be a valid match or a substitute ex
+pression.\n\n";
        redo;
    }
    my $tr = $regex =~ /^\s*(?:y|tr)\W/ ? 1 : 0;
    my $cap = $regex =~ /\([^?]/ ? 1 : 0;

    # This eval should fail on anything except a match, subst, or tr
    my $old_string = $string;
    eval "\$string =~ $regex";
    if ($@){
        print $OUT "$@\n\n";
        redo;
    }
    # Restore original after this eval
    $string = $old_string;

    # Variables declared in the eval must be escaped; those that aren'
+t
    # will be interpreted in the scope of the surrounding script.
    my $ret = eval qq%
        my \$match = \$string =~ $regex;
        my \$out = 'Matched: ' . (\$match ? "Yes" : "No");
        if (\@+ > 1 && ! $tr && $cap){
            \$out .= "\nCaptures:";
            \$out .= qq" [#\$_: '" . (\${\$_} || '') . "']" for 1 .. \
+$#+;
        }
        return "\$out\n";
        %;                      # End of eval

    print $OUT $@ ? "\nERROR: $@\n" : "\nResult: $string\n$ret\n";
    redo;
}
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In reply to Regex tester by oko1

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