It looks like the overflow still happens. (Expected result is different nowadays, since negative start positions are disallowed (see https://github.com/rakudo/rakudo/commit/fa3ce116e3).
See also http://irclog.perlgeek.de/perl6/2015-11-21#i_11577908 $ perl6-m -e 'say index("xxy", "y", -999999999999999999999999999999999999999999999999999999999999999)' Nil $ perl6-j -e 'say index("xxy", "y", -999999999999999999999999999999999999999999999999999999999999999)' Position in index out of range. Is: -9223372036854775807, should be in 0..3 in block <unit> at -e:1 Actually thrown at: in block <unit> at -e:1 There are fudged tests ('todo') for this in S32-str/index.t and S32-str/rindex.t. Also nqp-m and nqp-j still behave differently: $ nqp-m -e 'nqp::say(nqp::index("xxy", "y", -999999999999999999999999999999999999999999999999999999999999999))' -1 $ nqp-j -e 'nqp::say(nqp::index("xxy", "y", -999999999999999999999999999999999999999999999999999999999999999))' 2
