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And issue the request again. C<Apache2::Reload> does its job and we can
see that C<My::Utils> was reloaded (look in the I<error_log>
file). However the script still returns:

  the color is white

=head3 The Explanation

Even though F<My/Utils.pm> was reloaded, C<ModPerl::Registry>'s cached
code won't run 'C<use My::Utils;>' again (since it happens only once,
i.e. during the compile time). Therefore the script doesn't know that
the subroutine reference has been changed.

This is easy to verify. Let's change the script to be:

  #file:test.pl
  #------------
  use My::Utils;
  print "Content-type: text/plain\n\n";
  my $sub_int = \&colour;
  my $sub_ext = \&My::Utils::colour;
  print "int $sub_int\n";
  print "ext $sub_ext\n";

Issue a request, you will see something similar to:

  int CODE(0x8510af8)
  ext CODE(0x8510af8)

As you can see both point to the same CODE reference (meaning that
it's the same symbol). After modifying F<My/Utils.pm> again:

  -  sub colour { "red" }
  +  sub colour { "blue" }

and calling the script on the secondnd time, we get:

  int CODE(0x8510af8)
  ext CODE(0x851112c)

You can see that the internal CODE reference is not the same as the
external one.

=head3 The Solution

There are two solutions to this problem:

Solution 1: replace C<use()> with an explicit C<require()> +
C<import()>.

 - use My::Utils;
 + require My::Utils; My::Utils->import();

now the changed functions will be reimported on every request.

Solution 2: remember to touch the script itself every time you change
the module that it requires.

=head1 Threaded MPM and Multiple Perl Interpreters

If you use C<Apache2::Reload> with a threaded MPM and multiple Perl
interpreters, the modules will be reloaded by each interpreter as they
are used, not every interpreters at once.  Similar to mod_perl 1.0
where each child has its own Perl interpreter, the modules are
reloaded as each child is hit with a request.

If a module is loaded at startup, the syntax tree of each subroutine
is shared between interpreters (big win), but each subroutine has its
own padlist (where lexical my variables are stored).  Once
C<Apache2::Reload> reloads a module, this sharing goes away and each
Perl interpreter will have its own copy of the syntax tree for the
reloaded subroutines.


=head1 Pseudo-hashes

The short summary of this is: Don't use pseudo-hashes. They are
deprecated since Perl 5.8 and are removed in 5.9.

Use an array with constant indexes. Its faster in the general case,
its more guaranteed, and generally, it works.

The long summary is that some work has been done to get this module
working with modules that use pseudo-hashes, but it's still broken in
the case of a single module that contains multiple packages that all
use pseudo-hashes.

So don't do that.




=head1 Copyright

mod_perl 2.0 and its core modules are copyrighted under
The Apache Software License, Version 2.0.


=head1 Authors

Matt Sergeant, matt@sergeant.org

Stas Bekman (porting to mod_perl 2.0)

A few concepts borrowed from C<Stonehenge::Reload> by Randal Schwartz
and C<Apache::StatINC> (mod_perl 1.x) by Doug MacEachern and Ask
Bjoern Hansen.

=head1 MAINTAINERS

the mod_perl developers, dev@perl.apache.org


=cut