#!/usr/bin/perl

use warnings;
use strict;

my %refspecies = (
	HOMSAP => 'Homo sapiens',
	MUSMUS => 'Mus musculus',
	CIOINT => 'Ciona intestinalis'
	);

my @species =('HOMSAP','MUSMUS','-CIOINT');
my @duplicate = @species;

# Incorrect working code
print "Before processing: @species\n";

foreach (@species) {
	/^-?(.+)$/;
	$_ = $1;
	unless (exists $refspecies{$_}) { # Species not in list
		die "$_ is not in the species table\n";
	}
}

print "After processing: @species\n";

#Correct working code
#Duplicate run with minor code adjustment
print "Before processing: @duplicate\n";

foreach (@duplicate) {
	/^-?(.+)$/;
	#$_ = $1; Removed this line and changed $_ below in $1. This shouldn't matter because I am manipulating $_ in the code above and NOT @species, but somehow it does!
	unless (exists $refspecies{$1}) { # Species not in list
		die "$1 is not in the species table\n";
	}
}

print "After processing: @duplicate\n";

#Output is:
#Before processing: HOMSAP MUSMUS -CIOINT
#After processing: HOMSAP MUSMUS CIOINT
#Before processing: HOMSAP MUSMUS -CIOINT
#After processing: HOMSAP MUSMUS -CIOINT

# Look at @species element 3. Why is @species changed?