#!/usr/bin/perl
use strict;

local $\ = '-' x 40 . "\n";
eval { my $test = CGI::thisFunctionDoesNotExist() };
print $@;

eval { my $test = thisFunctionDoesNotExist CGI() };
print $@;

eval { my $test3 = new Some::Package::That::Doesnt::Exist() };
print $@;

# A function that does not exist in main::
functionThatDoesntExist('test');
exit;

sub UNIVERSAL::AUTOLOAD {
  my $method = $UNIVERSAL::AUTOLOAD;
    
  # So that we have the Carp methods without
  # cluttering up our UNIVERSAL namespace
  use Carp ();
    
  # First, if they are in the main namespace,
  # Fail, since we don't have a package to load
  if ($method =~ /^main::/) {
    Carp::croak("AUTOLOAD failed: $method");
  }
    
  # Else, split the name into package and method names
  my @methodParts = split('::', $method);
  my $methodName = pop(@methodParts);
  my $package = join('::', @methodParts);
    
  # Now, load the package.
  # Die if it fails
  eval "use $package";
  Carp::confess($@) if ($@);
    
  # If you made it here, do standard autoload stuff
    
  # Check which form of method call this is
  # This will catch the packageName::methodName format
  # The methodName packageName format is already good
  if ($_[0] ne $package) {
    unshift @_, $package;
  };
    
  no strict;
  # the goto call will pass along @_ transparently
  goto &$method;
};
[download]

This is an example run:

~johannz >./autoload.pl
Undefined subroutine CGI::thisFunctionDoesNotExist
----------------------------------------
Undefined subroutine CGI::thisFunctionDoesNotExist
----------------------------------------
Can't locate Some/Package/That/Doesnt/Exist.pm in @INC (@INC contains: /usr/bin/perl/lib/ .) at (eval 3) line 2.
BEGIN failed--compilation aborted at (eval 3) line 2.
        UNIVERSAL::AUTOLOAD('Some::Package::That::Doesnt::Exist') called at ./autoload.pl line 11
        eval {...} called at ./autoload.pl line 11
----------------------------------------
AUTOLOAD failed: main::functionThatDoesntExist at ./autoload.pl line 27
        UNIVERSAL::AUTOLOAD('test') called at ./autoload.pl line 15

I would never allow this code past a code review, but it does allow you to make method calls dynamically. Never again will you need to use the EVIL 'use' statement. Down with Clarity, Up with Obfuscation!!!

Note: This whole thing is an example of how perl gives you enough rope to hang yourself. I wanted to explore the possibilities of the what the UNIVERSAL class and AUTOLOAD methods make possible. Indigo was part of the inspiration for this during a talk over the cube walls