Hi, I am also a beginner, however, I have just realized what went wrong. You must have had the same problem. Your Perl program was written correctly, but it was more likely that your file that you wanted to open was not good. The file must be saved with WordPad and NOT with NotePad because with WordPad you can choose to save the files as "Text document-MS_DOS" format and if it is a peptide you also need to give a ".pep" extension. I hope it helps, let me know if it works now.