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I wanted to write a test to see if a given scalar contains a quoted regular expression. I don't care if the regex is valid or what it matches as long as perl thinks it's a real quoted regex. I discovered that it's either much easier than I thought, or I'm missing something. Or both :)

#!/usr/bin/perl
use strict;
use warnings;

my %qrs = (
    string1  => 'foo',
    string2  => '(xism)',
    regex    => qr/foo/,
    'regex?' => '(?-xism:foo)',
);

while( my( $key, $regex ) = each %qrs ) {
    print "'$key' ";
    print $regex =~ /\(\?\-xism:/
        ? 'YES: '
        : 'no: ';
    print $regex;

    print ' (and matches)' if 'foo' =~/$regex/;
    print "\n";
}

[download]

And here's the output:

'regex?' YES: (?-xism:foo) (and matches)
'regex' YES: (?-xism:foo) (and matches)
'string1' no: foo (and matches)
'string2' no: (xism)

It looks like creating a scalar of the pattern "(?-xism:$STUFF)" is enough to make perl believe it's a quoted regex. I've tried to find a definitive in perldoc, man pages, The Camel, etc. answer and haven't.

Is it really this cool and simple?


--
man with no legs, inc.

In reply to Walks like a regex, quacks like a regex... by legLess

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