Don't do it that way! The code is clearer and more maintainable (and actually works) if you:

for my $i ($i .. $#{$eventscores} ) {
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or:

for my $eventscore (@$eventscores} ) {
        $rider_id = $eventscore->[0];
        while ( $eventscore->[0] == $rider_id ){
            push (@scores, $eventscore->[2] );
            $i++;
        }
#...more code.. unrelated to loop
}
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as appropriate.