An addendum:

As a programmer, you can force all your translators to use UTF-8 in all
translated message catalogs. But you cannot force them to use ISO-8859-1
there. Because then Polish or Chinese translations become impossible.

The GNU .mo catalogs use the same encoding for msgids and msgstrs.
(Otherwise the translator would need a special editor for viewing the PO
file.)

As a consequence, you cannot use an ISO-8859-1 encoded string as argument
to __.

You can use an ASCII msgid ("Datei oeffnen"). This has the drawback that
you need an extra German catalog for mapping "Datei oeffnen" to
"Datei öffnen".

You can also use UTF-8 msgids. This has the side effect that all your
sources must be UTF-8 encoded. It has the advantage that you will leave
the ISO-8859-1 world behind you. But as Guido says:

> In Perl, the Unicode support starting with Perl 5.8 is a complete mess,
> and I would _never_ use any non ascii characters in the sources.  The
> way the Perl interpreter processes your source code is for sane human
> beings impredictable, because it will sometimes convert even source code
> from the assumed input character set to the guessed ouput character set.

so this option is impractical with Perl source.

Bruno