Count the capture groups in a qr regex?

Question

I am working on a project which at one point gets a list of files from an ftp server. At that point it either returns an arrayref of files OR if an optional regex reference

Answer 1

You could use YAPE::Regex to parse the regular expression to see if there is a capture present:

use warnings;
use strict;
use YAPE::Regex;

filter_files(qr/foo.*/);
filter_files(qr/(foo).*/);

sub filter_files {
    my ($pattern) = @_;
    print "$pattern ";
    if (has_capture($pattern)) {
        print "yes capture\n";
    }
    else {
        print "no capture\n";
    }
}

sub has_capture {
    my ($pattern) = @_;
    my $cap = 0;
    my $p = YAPE::Regex->new($pattern);
    while ($p->next()) {
        if (scalar @{ $p->{CAPTURE} }) {
            $cap = 1;
            last;
        }
    }
    return $cap;
}

__END__

(?-xism:foo.*) no capture
(?-xism:(foo).*) yes capture