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sub Invoker::first    { shift; &first_callback }
sub Invoker::last     { shift; &last_callback }
sub Invoker::AUTOLOAD { -1 }
...
  my $name = shift; 
  Invoker->$name(@_); 
}

use strict;
use warnings;

...
   my $rc = invoker( $name, $name . '-arg' );
   print "$name: rc=$rc\n";
}