What do the new string methods in the LR 13.2 SDK do?

The LR 13.2 SDK on Mac provides many new string methods:

findx, gfind, gmatch, gmatchx, gsubx, ifind, ifindx, igmatch, igmatchx, igsub, igsubx, imatch, imatchx, matchx

The "i" versions (e.g. ifind()) appear to ignore case, e.g. ifind() is the case-ignoring version of find(). But what do the "g" and "x" versions do? (E.g. findx() and gfind()?)

Also, none of these are available in the Windows LR 13.2 SDK. 

@Rikk Flohr: Photography, perhaps you could ask the developers about this?