year validation

#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

my $year = qr{
    (?<year>
        (?<century> 1 [6-9]) (?<decade>[0-9]{2}) |
        (?<century> [2-9] [0-9]) (?<decade> [0-9]{2})
    )
}x;

for my $s (1984, 2009) {
    my @parts = $s =~ $year;
    print "for $s parts are ", join(", ", map { $_ // "undef" } @parts), "\n",
       "year is $+{year}, century is $+{century}, and decade is $+{decade}\n";
}