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?