Summarizing File 1 contains Field1 Field2 Field3 Field4 Field5 File 2 contains Field1..Field15 I need to compare Field11 from file 2 with field1 from file 1 and if match add Field5 from file1. If it doesn't match I need to print the line in any case. The problem is to print the line to file regardless of the match, since the code I posted above.....it will write the line as many times as they key I have in the hash obtained from file 1 I hope to have been clearer. Thanks for your idea!