Pattern Matching

Here's a postal code checker written in Perl:

$postalcode = "H3G 1V7";
if ($postalcode =~
    s/^([A-Z][0-9][A-Z]) ?([0-9][A-Z][0-9])$/$1$2/)
{
    print $postalcode;
}
else
{
    print "Invalid postal code: ", $postalcode;
}