#!/usr/bin/perl -w
use strict;
 
my $var = "WooHoo\n";
 
# I know that this will print ...
print $var if $var =~ /^Woo/;
 
# and I know that this will print ...
print $var if $var !~ /^Hoo/;
 
# and I think I understand whats
# going on here ...
$var =~ s/W/H/;
print $var;
 
 
# But I didn't expect this ...
$var !~ s/H/W/;
print $var;