$/ = "";
while (<DATA>) {
    s/^(.*)\n//;
    $key = $1;
    s/\n==(?=\n)/\n/g;
    $structure{$key} = $_;
}

__DATA__
key1
Here's a text block including blank lines ("encoded" as "==" in the perl script):
==
and here's a part of the block that's enclosed within "blank lines"
==
and here's the last part of the value for key1.

key2
blah blah
etc.