#!/usr/bin/perl -w
# shift_decode.pl - Don Yang (uguu.org)
#
# Decode text using constants found with shift_constants.c

use strict;
use constant BOUNDARY => 40;
use constant MUL1 => 3;
use constant MUL2 => 255;
use constant SHIFT => 158;

# Decode input
my $input = join '', <>;
foreach my $c (unpack 'C*', $input)
{
   print chr(($c * ($c < BOUNDARY ? MUL1 : MUL2) + SHIFT) % 256);
}