Just to make it more clear:
Status quo: 

use Math::RungeKutta;

sub outer {
   my $var = sub_from_other_package();
   no warnings qw(closure);

   sub differ {
      my $y = shift;
      $var->[...]{...}{...}; etc.
      ...
      return $res;
   }

   sub dydt {
      my ($t,@y) = @_;
      return differ($y);
   };

   ($t, @y) = rkXXX(\@y, \&dydt, $t, $dt);

}

[download]
Neither local nor subs declared in lexicals help me out of my misery. The former is undefined the next is used as ""-ref. So There is a bug but what could it be that turns a sub into undefined?
Hope you still with me and not bored ;)

In reply to Re^3: Closures and undefined subs by Anonymous Monk
in thread Closures and undefined subs by Anonymous Monk

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