The -B keyword

-B is a file test that tests, if the file is a "binary" file (opposite of -T).

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 $_. -B 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).

  -B DIRHANDLE
  -B EXPRESSION
  -B FILEHANDLE
  -B FILENAME
  -B