As soon as I read your error message I thought, "how do you know you opened F in the first place?" Then I read the rest of your question and the other responses and realized that the globbing issue was the primary problem. Nonetheless, you should always check the return value of open to make sure it succeeded. If open fails, you will get the same error (print() on unopened filehandle F) when you try to print to the filehandle later.

open, perlopentut