sub bits { glob join "", map "{0,1}", 1..$_[0] }
say for bits(10);
__END__
0000000000
0000000001
0000000010
0000000011
0000000100
0000000101
...
1111111011
1111111100
1111111101
1111111110
1111111111

##</code><code>##

sub bits { glob "{0,1}" x $_[0] }