Use appropriate markup (see Writeup Formatting Tips) and preview your node to check that the result is as you expect it.

Show us the actual code (copy and paste is your friend) that generated the error and, if it's in a sub, show us the calling code too.

If you want us to make the effort to help you, you need to make the effort to describe your problem clearly and accurately.

The key issue (as already implied by Marshall and discussed by JavaFan) is that you should probably be using my in your open to create a lexical file handle. If there is a bigger issue, you haven't told us about it!