#!/usr/bin/perl
@VALUE = split (/\//, $ARGV[0]);
@OCTETS = split (/\./, $VALUE[0]);
$calculated = 2**(32 - $VALUE[1]);
$OCTETS[3]--; # (base counts as one...)
$OCTETS[3] += $calculated;
$broadcast = join (".", @OCTETS);

print qq~
$calculated hosts
Base is $VALUE[0]
Broadcast is $broadcast~;