Here's one way:

use warnings;
use strict;

local $/ = 'Message dump:';

while (<DATA>) {
  chomp;
  print;
}

__DATA__
Message dump:
1=4 11:13:2006
Message dump:
1=445=3=56=23=67=23=123=12=34
11:13:2006
Message dump:
[download]

Prints:

1=4 11:13:2006

1=445=3=56=23=67=23=123=12=34
11:13:2006
[download]

Update - that loop was a little verbose. It crunches down to:

chomp, print while <DATA>;
[download]