# If you want to output to STDOUT and to the file,
# create a handle which may point to STDOUT.

if ($filename) {
   open(FILE, '>', $filename)
   or die("Can't open $filename: $!\n");
} else {
   open(FILE, ">&STDOUT");
   or die("Can't dup STDOUT: $!\n");
}

print FILE (...);  # Goes to file if one was specified, else STDOUT.
print(...);        # Goes to STDOUT.