open my $if1, '<', $input_f1 or die "Can't open $input_f1: $!\n"; open my $if2, '<', $input_f2 or die "Can't open $input_f2: $!\n"; while(<$if1>) { # Read each line of file1 my $line = $_; chomp($line); my ($key1, $vf1, $vf2) = split(/\*/, $line); seek($if2, 0, 0); # Make sure file handle point to the beginning of the file while (<$if2>) { # Read each line of file2 my $line2 = $_; chomp($line2); my ($key2, $value) = split(/\*/, $line2); if ($key1 eq $key2) { $vf1 = $value; } else { $vf1 = ' '; } } }