It should be noted (somewhere) that once a page difference is detected, it continues to be announced (every x minutes) as long as the page is different from the original at the time the script was launched.
And then there's the possibility that if the content of the page changes back to the original, the announcements will cease.
Therefore the user will have to stop the script and restart it if she wants to detect another page change.

One thing I would do is put the page getter/digester into a subroutine:

  sub page_hash {
    my $d = Digest::MD5->new();
    $d->add( get( PAGE ) );
    $d->digest
  }
[download]

Then you can say

my $original = page_hash();
. . .
  if ( $original ne page_hash() )
    . . .
[download]

jdporter
The 6th Rule of Perl Club is -- There is no Rule #6.