Short answer: Don't use named subs inside of the other subs. 

use warnings;

sub outer {
   my ($var) = @_;

   sub inner {
      print("$var\n");
   }

   inner();
}

outer("abc");
outer("def");

[download]
Variable "$var" will not stay shared at line 7.
abc
abc

[download]

Update: Solution: 

use Math::RungeKutta;

sub outer {
   my $var = ...;

   my $dydt = sub {
      ... $var ...
   };

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

[download]

You could local *dydt = sub { ... }; and \&dydt, but it's extra work for nothing here.

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

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