#!/usr/bin/perl -w
use strict;

my $string = 'abcbar';
my $sub = get_backref( $string );

print $sub;

sub get_backref {
	my $string = shift;
	my $regex  = '(foo)|(bar)|(baz)';
	my $backref = 0;
	
	# This is the number of possible backreferences
	# It's easier to set than generate dynamically
	my $limit = 3;
	local ( $1, $2, $3 );

	$string =~ /$regex/;
	for ( 1 .. $limit ) {
		no strict 'refs';
		$backref = $_, last if defined $$_;
	}
	return $backref;
}

##</code><code>##

#!/usr/bin/perl -w
use strict;

my $string = 'abcbar';
my $sub = get_backref( $string, 3, '(foo)|(bar)|(baz)' );

print $sub;

sub get_backref {
    my ( $string, $num_refs, $regex ) = @_;
    my $backref = 0;

    # This is the number of possible backreferences
    # easier to set than count
    my $local_brefs = '';
    for ( 1 .. $num_refs ) {
        $local_brefs .= "\$$_,";
    }
    chop $local_brefs;
    my $code = <<"    END_OF_CODE";
    local ( $local_brefs );

    \$string =~ /$regex/;
    for ( 1 .. $num_refs ) {
        no strict 'refs';
        \$backref = \$_, last if defined \$\$_;
    }
    END_OF_CODE
    eval $code;
    return $backref;
}