If you want to make changes to the number or types of arguments that sieve_range() accepts, you'll have to make those changes in XS.xs and rebuild Math::Prime::Util.
The file 'sieve.c' contains a function named _sieve_range() which, AFAICS, is a separate function to sieve_range().
The _sieve_range() function seems to be a function that is private to 'sieve.c'.
I suggest contacting the Math::Prime::Util author regarding any changes you would like to see.