#! perl -slw use strict; my $mask = hex($ARGV[0]); print $mask; print unpack 'H*', pack 'C', $mask; my $setbits = unpack("%32b*", pack 'C', $mask ); printf("0x%x has %d set", $mask, $setbits); __END__ C:\test>junk 0xff 255 ff 0xff has 8 set