use strict;
use warnings;

BEGIN {
	package JIT;  # Just In Time evaluation
	$INC{'JIT.pm'} = __FILE__;
	
	use base 'Exporter';
	our @EXPORT = 'jit';
	sub jit (&) { bless $_[0] }
	
	use overload
		q[""]    => 'evaluate',
		q[0+]    => 'evaluate',
		q[bool]  => 'evaluate',
		fallback => 1;
	sub evaluate { $_[0]->() }	
};

use JIT;

my $foo = "hello";
my $y;  # needs to be declared, but we haven't assigned a value to it yet.
my $x = jit { "$foo".$y }; # $y is not yet defined.
$y = "world";              # now define $y
print $x;