my $mask = hex($ARGV[0]);

print $mask;
print unpack 'H*', $mask;

my $setbits = unpack("%32b*", $mask);

printf("0x%x has %d set", $mask, $setbits);

##</code><code>##

C:\test>junk 0xff
255    ## 3 bytes
323535 ## 6 nybbles with bit patterns 0011 0010 0011 0101 0011 0101 
0xff has 11 set

##</code><code>##

#! 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