#!/usr/bin/perl -w

my $data = 'reference.txt'; 
open INFILE, '<', $data;

while(<INFILE>)
{
   
   my $line = $_;
   
   chomp($line);
   
    my ($id, $description) = split /\t/, $line, 2;
    
	my $data2 = "readthisfile.txt";
	open INFILE2, "<", $data2;

	while(<INFILE2>) {

					my $line2 = $_;
					
					chomp($line2);
	
					$line2 =~ s/$id/$description/g;
						
					}
}