[tex-hyphen] hyphenation different in xelatex?

[Philip Taylor]

Reinhard Kotucha wrote:

> And pdftex is 100% backwards compatible with DEK's TeX.

Well, not really : compare the result of expanding (e.g.,)

	\expandafter \ifx \csname pdfximage\endcsname \relax UNDEFINED\else
DEFINED\fi

in the two engines ...

** Phil.