#!/usr/bin/perl -w

use strict;

sub do_this { print "doing this!\n" }
sub do_that { print "doing that!\n" }

my $code = get_coderef('do_this');
$code->();
$code = get_coderef('do_that');
$code->();
$code = get_coderef('do_nothing');

if (defined($code)) {
    $code->();
} else {
    print "Not defined!\n";
}