use warnings;
use strict;

sub func {
    my ($x, $y) = @_;

    _validate($x, $y);
    print "$x, $y\n";
}
sub _validate {
    my ($x, $y) = @_;

    die if $x <= 20;
    die if $y !~ /^\w\d{2}/;
    die if length $y > 10;
    die if $y =~ /y/;
}