Here's a puzzler. I am trying to write a script which can handle plugins, so that installing a plugin is as easy as downloading it and putting it in a specific directory - the script will automatically detect and use it at several points.

One requirement is security: I think this is satisified by making sure the directory can only be written to by the owner of the script, so if he/she puts stupid stuff in there, that's his or her fault. Another requirement, pulling the other way, is future-proofing: it should be able to handle upgrades and plugins I haven't thought of yet. A final requirement is ease of use: no renaming stuff, no command line fiddling, just download and go.

My initial thought is as follows:

• Create a module handling script. This "require"s all the files in the plugin directory. It then executes the relevant subroutines in those files (see below).
• The original script calls the module handler at several defined points. The module handler knows where it is being called from.
• Each plugin script will consist of a hash of switches, plus some subroutines. E.g.:

  $can_be_called_from = { 
     foo => 1,
     bar => 0,
     baz => 1
  };
  
  sub foo { ... }
  sub baz { ... }
  
  1;
  [download]

• When called, the module handler checks each script for the relevant switch:

  foreach ($plugin_script) {
     require $_;
     if ($plugin::can_be_called_from->{$where_I_was_called_from}) {
        #call the relevant subroutine
     }
  }
  [download]

I have some worries about this.

(1) Is it really secure?

(2) I don't seem to be using the Perl module system very effectively, except to distinguish between different plugins' $can_be_called_from hashes.

Can anyone suggest an improvement, or some useful thoughts about this architecture problem? Either Perl-specific comments, or general ideas, are welcome.

Cheers,
Dave

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