Something

for (my $n=0;;$n++) {
    words("",$n);
}


sub words($$) {
    my ($s,$k) = @_;
    if (length($s)<=$k) {
	foreach my $l ("a".."z") {
	    words($s.$l,$k);
	}
    } else {
	print "$s\n";
    }
}