#!/usr/bin/perl use warnings; use strict; my %bow1 = (); my $file1 = shift; open (FILE1, "$file1")or die "could not open FILE1:$file1; # Open first file while () { my ($ID1, undef, undef, undef, $Seq1) = split; $bow1{$ID1} = $ID1; # your id is the key and can be got again } close FILE1; my $file2 = shift; open (FILE2, "$file2")or die "could not open FILE2:$file2"; # Open second file while () { my ($ID2, undef, undef, undef, $Seq2) = split; if(defined($bow1{$ID2})){#IDs Match if($bow1{$ID2} eq $Seq2){ #both match so remove from the hash to avoid looking for a correct one later delete $bow1{$ID2}; }else{ #id's dont match print "IDs exist but dont match ID:$ID2:Seq1:$bow1{$ID2}:Seq2:$Seq2:\n"; } }else{ #id not in list 1 print "ID only in file 2 ID:$ID2:$Seq1\n" } } close FILE2 #run through any remaing list one items that werent matched while((my $key,my $value) = each %bow1){ print "ID only in file 1 ID:$key:Seq:$value:\n"; }