poxhtml is a tool to help translate XHTML files. It can do two things:

1) Translate an (English) XHTML file to another language based on
a database of translated phrases provided in a PO file.

2) Generate a POT file (a PO file with empty translations) from an
XHTML file. The POT file can then be given to a translator to make a
PO file.

The full manual is included in the program: see the source or run
"perldoc poxhtml".

The PO/POT format is the format of GNU gettext. It is defined in
https://www.gnu.org/software/gettext/