You are right that the error is the $self-> in the sub call. Lets see what it's doing

&{                            # call the result of the block as a sub
  $self->{                    # lookup in hash $self the result of
          $dispatch{$command} # lookup $command in %dispatch
         }
 }();                         # call the sub with no arguments
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I am guessing you want to call the sub, passing $self, which should be

 &{$dispatch{$command}}($self);
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