#open file1, split each line delimited by comma and read into %hash
#assume $code, and $description are the key/value pairs of the %hash.

#open file2 and read into array
while <file2> {
my @array2 = <file2>;
}
#close file2

#open file2
foreach $item (@array2) {
 @values = split /,/;
 $values[4] = $hash{$values[2]}; # this should now put the new description from the hash

 print file2 $values[1], ", ", $values[2], ", ", $values[3], ", ", $values[4], ", ", $values[5], ", ", "\n";
                                 # writing the line back into file2
}