First, thank you for trying to answer my question rather than dissuade me from doing what I'm doing. :)

I realized that moving the __DATA__ line would cause problems, and posted another snippet deep in my stack of replies to ikegami above:

my $code = join '', <DATA>;
seek DATA, 0, 0;
while (<DATA> !~ /^__DATA__$/) {}
[download]

This code does what I want. I feel a little better about whether I'm stomping on internals, too. I'm going to use it.

As you identified, this approach is going to be used on plugin-style code.