#! perl -slw
use strict;

sub gen {
	my( $len, $depth ) = @_;
	return () unless $len;
	return map {
		my $pre = $_;
		( $pre, map{ $pre . $_ } gen( $len -1, $depth )  );	
	} 0 .. $depth - 1;
}

print for gen( 4, 3 );