access to matched text

[mndrix]

This is different than access to the captures. Specifically, Vyacheslav wants this

from string '99 bottles of Beer' and pattern '[0-9]+ [a-z]+' get the string '99 bottles' or her position and length (1, 10)

I don't think this should be part of =~/2 so it should be part of the lower level interface. At the same time, look at pcre's and re2's interface to see what they make available about matched text.

[mndrix]

I've decided that this is not need because issue #1 allows one to wrap the pattern in a capture to get the same results:

?- regex('([0-9]+ [a-z]+)', '99 bottles of Beer', [Matched]).
Matched = '99 bottles'.