$can_be_called_from = { 
   foo => 1,
   bar => 0,
   baz => 1
};

sub foo { ... }
sub baz { ... }

1;

##</code><code>##

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