I put

# po plugin
po_master_language => 'en|English',

po_slave_languages => [ 'zh|Chinese']

in page.setup. And did

$ikiwiki --setup ./page.setup

but get errors:

Can't use string ("en|English") as a HASH ref while "strict refs" in use at /usr/share/perl5/IkiWiki/Plugin/po.pm line 162.

Line 162 of the file reads

delete $config{po_slave_languages}{$config{po_master_language}{code}};;

What's wrong? How to fix it?

You seem to be using an older version of ikiwiki. Either use a hash ref (see old documentation) or upgrade.
Comment by intrigeri Tue Dec 20 05:34:56 2011