# delete $file if it's not been modified for 15 minutes
if ( (stat $file)[9] < time() - (3600 / 5) ) {
    unlink $file;
}

##</code><code>##

Use of uninitialized value in numeric lt (<) at line 12 (#1)
 (W uninitialized) An undefined value was used as if it were already
 defined. It was interpreted as a "" or a 0, but maybe it was a mistake.
 To suppress this warning assign a defined value to your variables.