$$thr=threads->create(\&position,$text,$pattern);
        $$thr->join();
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That looks like you're:

1. Starting a new thread
2. waiting for it to end
• waiting for it to initialize
• waiting for it to do the work
• waiting for it to clean up
3. Getting the result.
4. Loop back to 1

That kind of thing is going to slow down your program with all the thread overhead. You need to create a small set of worker threads, and distribute the work between them.