use v5.10;
use strict;
use warnings;

sub delayed (&) {
	package delayed;
	use overload q[""] => sub { $_[0]->() }, fallback => 1;
	bless shift;
}

my ($person, $thing);
my $string = delayed {"Look $person, no $thing!"};

$person = "Ma";
$thing  = "stringy eval";

say $string;