It's very hard to tell what you want. Are you trying to return \&Web::Config::destination where Web::Config is dynamic?

sub SetDestination {
   my ($self, $class) = @_;
   $self->{destination} = do {
      no strict 'refs';
      \&{"${class}::destination"}
   };
}

sub ... {
   my ($self, ...) = @_;
   ...
   $self->{destination}->(...);
   ...
}
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In any case, this is poor design. Why not just pass $config?

sub SetDestination {
   my ($self, $config) = @_;
   $self->{config} = $config;
}

sub ... {
   my ($self, ...) = @_;
   ...
   $self->{config}->destination(...);
   ...
}
[download]