You can't get there from here

Ouch

Here's source code for a function I'll call ouch:

     my $ouchcode = "sub {       
                       use Acme::HaltingProblem;
                       my $arg = shift;
                       if (halts($arg, $arg)) { 1 while 1 }
                       else                   { return }
                    }";

It is expecting to get some program source code as its argument
- Then it asks if that program will halt when given its own source code as input
Now let's do

        my $ouch = eval $ouchcode;
        $ouch->($ouchcode);

We're giving the ouch function its own source code as input
What does it do?