OK, to really dig this (I think it's neat, and I'm pretty wantonly hyper-critical when it comes to Perl Poetry,) ya gotta know that it's a reference to the following haiku by the master nipponese poet Basho:

Mossy pond;
frog coming in-
splash!
[download]

Another, slightly more haiku-ish (and, for that matter, slightly less subtle) translation of this same verse is:

When the old pond
gets a new frog
it's a new pond.
[download]

There's a pretty good short overview of haiku (and Basho) here

Also, while we're on the subject, my fave Basho ditty is

The first cold showers pour.
Even the monkey seems to want
a little coat of straw.
[download]

The Autonomic Pilot