Accepting input for $date should be written as

  my $date = shift || '12/DEC/2001:17:23:09';
[download]

The means you can enter a value on the command line without having to edit your script, and if nothing is supplied a default value will be used.

The creation of the %month hash is better written using the pair operator =>. Also, since you never modify it, it is even better to define it as a constant. And finally, through the wonders of human perception finding it easier to scan columns, the betterer way would be something like:

  use constant MONTH => {
    Jan => 1, Apr => 4, Jul => 7, Oct => 10,
    Fen => 2, May => 5, Aug => 8, Nov => 11,
    Mar => 3, Jun => 6, Sep => 9, Dec => 12,
  };

  ...

  my $mon = MONTH->{$mon};
[download]

Minor usability quibble: programs that gratuitously clear the screen make me want to reach for the bazooka. Don't do it, or at least do it in a portable way, and don't do it if the code is not being run from a tty.

--

g r i n d e r
just another bofh

print@_{sort keys %_},$/if%_=split//,'= & *a?b:e\f/h^h!j+n,o@o;r$s-t%t#u';