gistfile1.txt

my $id = 'ZywYdtlIl8amEGe-Rq8xTg';

use MIME::Base64;


    $id =~ tr{_-}{+/};
    $id .= 'AA';
    my $bin_id = decode_base64($id);
    my $hex_id = unpack("H*", $bin_id);
    $hex_id =~ s/0{3,4}$//;
#    print $hex_id

    my @parts = ($hex_id =~ m/^((.{2})(.{2}).+)/)[1,2,0];

print map "$_\n", join '/', @parts;