To be honest, I don't understand your data structure. ;-) But from what I can tell, you're mixing arrays and hashes a tad indiscriminately. If nothing else, this won't do what you seem to be expecting: $info->{subdirectory}->{file}->[measurement] = INDEX; If the last item is an array [], then measurement better be an expression that returns an integer.

However, I think I see an easy way up for you. Get thyself over to CPAN, and look at Class::Struct. It lets you set up nested data structures that may be familiar to you, coming from a C/C++ background.

HTH ... a little