use strict;
use warnings;

doShift (2, 5);
print "\n";
doShift (3, 6);
print "\n";


sub doShift {
    my ($ones, $bits, $pattern, $limit) = @_;
    
    --$ones;
    $limit ||= $bits;
    $pattern ||= 0;
    
    for my $right ($ones .. $limit - 1) {
        if ($ones) {
            doShift ($ones, $bits, $pattern | (1 << $right), $right);
        } else {
            printf "%0*b\n", $bits, $pattern | (1 << $right);
        }
    }
}