At a guess your reference to a subroutine in the current package is a string naming the subroutine, in which case you are doing a symbolic lookup. That breaks when the lookup is done in another package. The simplest way to check that is through use strict, which will catch the error up front rather than through allowing subtle bugs in your code and understanding survive. That said, here is a working example:

package Foo;
use strict; # Always

sub foo {
  (shift)->(); # Call the function passed in by reference
}

package Bar;

sub bar {
  print "This is bar\n";
}

Foo::foo(\&bar); # Pass a ref to a sub to another package
[download]

generally, it's a good idea to post the code that you're using along with your question. It's possible that the problem is somewhere other than where you think it is.

Also, lots of us are lazy, and really don't want to write code to test what you want us to test. Debugging existing code is another matter entirely... :)

-Ton

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The power of man...