The -k keyword edit
-k is a file test that tests, if the file has its sticky bit set.
It takes one argument, either a FILENAME, a FILEHANDLE, or a DIRHANDLE to test the associated file to see, if something is true about it. If the argument is omitted, it tests $_. -k returns 1 for true and an empty string for false. If the file doesn't exist or can't be examined, it returns undef and sets $! (errno).