my $filename = "edges.txt";   #Set a variable for our file name
open(my $fh, "<", $filename) or die "Can't open file $filename.";  #Open the file edges.txt
	while (<$fh>) {
  	if ($_ =~ m/(\S+)\t(\S+)/) {           #Match the IDs in the file to $1 and $2
		$edge{$1,$2}= $holder;             #assign IDs as format $edge{ID1,ID2}
close $fh;   #Close the file edges.txt
   my @list = keys %uniqedge;
   print "@list\n";          #Prints the list of keys, but they are uni-directional (i.e. repeated for ID1-ID2 and ID2-ID1)