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

my $str;

$str = 'abc def 12';
$str =~ /(\d+)/;
print "$1\n" if ($1);

$str = 'foo';
$str =~ /(\d+)/;
print "$1\n" if ($1);

if ($str =~ /(\d+)/) {
    print "$1\n";
}
else {
    print "no match\n";
}