My bad, should have been
LC_ALL=C PERLLIB=../lib perl ../po4a-gettextize -f latex -m data-24/simple.tex
np (and I could have figured that out myself), output is attached.
I tried with perl-5.14.4 and 5.18.0, same result (but the date of the POT file as it took
me 5 minutes to switch perl versions :-)