Are you talking about a callback function that needs to keep track of some state, as in this example: 
our $count = 0;
sub my_callback {
  warn "I've been called ".(++$count)." times\n";
  ...
}
my $thread = threads->create(..., \&my_callback);
$thread->join;

print "count = $count\n"; # prints 0

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And the issue that this won't work in a threaded-environment because the $count that gets updated is only accessible in one thread (since it is not declared as shared.) So, callbacks have to be thread-aware if they are going to be used in a threaded environment.

Interesting problem...

In reply to Re: Thread-safe modules and callbacks by pc88mxer
in thread Thread-safe modules and callbacks by Saladino

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