ikegami may have nailed it; he usually does. But many others, /me included, would be more likely to be able to help were you to provide us with a specific sample of your "text file that has perl variables..." and (a minimal version of) the code you're using.

Please see On asking for help, How do I post a question effectively? and I know what I mean. Why don't you?. What's more, if you have not done so already, please read and heed Markup in the Monastery -- or, at least pay attention to the instructions on the use of paragraph and code tags which appear below the text input box when creating a node.