gistfile1.pl

#!/usr/bin/env perl

package Probe;
use Scalar::Util qw/ set_prototype /;

sub create_function {
	my ($answer) = @_;
	*Probe::block = sub (&) {
		shift->($answer);
	};
	set_prototype(\&Probe::block, '&');
}

package main;
BEGIN {
	Probe::create_function(42);
}
Probe::block { print "the answer is $_[0]\n" };