#!/usr/bin/perl
# vi:ts=4 sw=4 et:
use strict;
use warnings;

my $string = 'FOO1 BAR FOO2';

my @regex = (
    qr{(BAR)?},
    qr{(BAR)?.*},
    qr{\s(BAR)?.*},
    qr{.(BAR)?.*},
);

for my $r ( @regex ) {
    my ($m) = $string =~ $r;
    printf "%8s : %s\n", ($m || 'no match'), $r;
}