Recursive closure

Discussion

$fib = 7;   # Should "Bang!" here

Here you explicit break the circular reference. If you let $fib fall out of scope without explicitly breaking the circular reference the closure would not be destroyed (until global destruction). ( Lukas Mai's exposition.)

Using assignment to break the circular reference like this is very much a second-class approach.

• On aesthetic/maintainability grounds you really want whatever you have do to prevent the leak to be lexically close to the declaration of $fib.
• On the general case you have to ensure that all exit paths (last, next, die, return) pass though the statement where the circular reference is explicitly broken.

In practice this mean that if you want to avoid weak references or local() then you have to put the assignment in an AtExit object.