The delimiter should depend on the data. If you know you are not using tabs or commas, use them for delimiters. If you know you are not going to use the string "KJBLDGL45W89Y0SDFAHKSDAFPOIU3WE8Y9", use that as a delimiter. Or maybe use '<(-^.^-)>' x 100; -- you get the idea.

I think we would need more information about the data you are trying to delimit in order to suggest the best delimiter.

Oh, and, just to cover some more bases, if you are searching for a delimiter for 'Perl', I would go with '' to be safe ;) (assuming you want each character).