[perl #125784] Negative overflow in Str.index $startpos

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# New Ticket Created by  Alex Jakimenko 
# Please include the string:  [perl #125784]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=125784 >


Code:
say index 'xxy', 'y',
-999999999999999999999999999999999999999999999999999999999999999;
say index 'xxy', 'y',
-9999999999999999999999999999999999999999999999999999999999999999;

Result:
Nil
2