#!/local/bin/perl
use strict;
use warnings;

my %hash;
my $holder = "";  #used because it was asked of me

open (EDGES, "<edges.txt") or die "Failed to open edges.txt.\n";
while (<EDGES>){
    chomp ($_);
    if ($_ =~ m/(\S*)(\t)(\S*)/) {
	    $hash{$1,$3} = "$holder";
}}

#below isn't needed, just ensures I populated the hash correctly

my $key;                           
   foreach $key (keys %hash){
	print "$key\n";
}