In addition to ww's suggestions, you may want to choose an easier to read and more maintainable way for allocating resources according to difficulty level. Instead of all those ifs/elsifs, maybe try something like:

#!/usr/bin/env perl
use v5.10; # or later!
use warnings;
use strict;

my ( $diff, $wood, $food );
$diff = "easy"; 

#consider given/when instead of ifs...
given ($diff) {
    when (/easy/) { $wood = 120 ; $food = 50; }
    when (/hard/) { $wood =  75 ; $food = 20; }
}

say "I have $wood sticky sticks!";
say "I have $food delicious morsels!";

__END__
I have 120 sticky sticks!
I have 50 delicious morsels!
[download]

Adding a new difficulty level or resource-type into this structure is $diff eq "easy"; (of course, if you add more resources, you should probably adjust the formatting so they aren't all on one unreadable line...)