  # In myscript.cgi, or your mod_perl configuration, or wherever:
  
  # This could be relative to the script path or config file
  my $plugin_dir = '/opt/myscript/plugins'; 
  
  sub load_plugins {
    # Read in the names of all .pm or .pl files in the plugins dir.
    # (Even better would be a recursive search of subdirectories.)
    unless ( opendir(PLUGINDIR, $plugin_dir) {
      warn "Plugin dir '$plugin_dir' is missing or unreadable.";
      return;
    }
    my @filenames = grep /\.p[ml]/, readdir(PLUGINDIR);  
    closedir(PLUGINDIR);
    
    # Put the plugins directory in our library search path.
    # This allows one plugin to use or require another one.
    local @INC = ( $plugin_dir, @INC );

    # Try to load all of the plugin files, but don't die trying.
    foreach my $plugin ( sort @filenames ) {
      eval "require $plugin";
      if ( $@ ) {
	warn "Skipping plugin $plugin: $@"
      }
    }
  }

  sub print_output {
    print @_;
  }

  load_plugins();
  print_output( "<html>Here's my CGI script output.</html>" );


##</code><code>##

  # In $plugins_dir/uppercase.pm:
  
  sub print_output {
    print map { uc } @_;
  }

##</code><code>##

  # In $plugins_dir/uppercase.pm:
  
  my $inner_print_output; 
  BEGIN { $inner_print_output = \&print_output }
  
  sub print_output {
    &$inner_print_output( map { uc } @_ );
  }

##</code><code>##

  # In $plugins_dir/remove_whitespace.pm:
  
  my $inner_print_output; 
  BEGIN { $inner_print_output = \&print_output }
  
  sub print_output {
    &$inner_print_output( map { s/\s//g } @_ );
  }