Well, as the errormessage says: can't use ... while "strict refs" in use.

You want to use symbolic references, which are not allowed when you use strict.

You could add the line no strict refs; to your program, which would make it work.
But the better solution would be to use a hash for things like that.

Use Super Search with 'strict' and 'refs', it will give you loads of nodes on that topic.