See perldoc -f -X. What you want is the -s test. -s FILEHANDLE will return the (nonzero) size of the file referred to by FILEHANDLE. That won't help you if you're on a Unix machine, though. (On my box here, the directory size is 1024 -- that's a feature of the particular filesystem.) You might also look at the modification time test (-M FILEHANDLE). It returns the age of the file when the script started.