[XeTeX] [tex-hyphen] Hyphenation of polytonic Greek (expressed in Unicode)

[Philip Taylor]

Just to follow up on a thread started on the "TeX-Hyphen" list,
where does one learn exactly what \XeTeXlinebreaklocale does ?
TeXdoc XeTeX tells me :

> \XeTeXlinebreaklocale ‹Locale ID›
> Defines how to break lines for multilingual text.

but having read that, I am no wiser than I was before,
except that I now know that \XeTeXlinebreaklocale exists ...

** Phil.