[pcre-dev] Oniguruma subroutines

Was trying out some subroutine patterns hoping to learn how to use them.

This pattern (which works) is cited in pcrepattern:

(abc)(?i:\g<-1>)

but the documentation also says that case sensitivity can't be
controlled in the subroutine call.

so I tried:

(abc)(\g<-1>)

and got a compilation error, that a recursive call could loop
indefinitely. (?)

This works:
(abc)(\g<1>)

Does the compilation error above make sense?

Thanks,
Sheri