Spotted this in the release notes:
<para>
Add extension <application>bool_plperl</application> which transforms
<acronym>SQL</acronym> booleans to/from PL/Perl booleans (Ivan
Panchenko) WHERE IS THIS DOCUMENTED?
</para>
bool_plperl is documented in "44.1. PL/Perl Functions and Arguments", but not
with a separate section (which fwiw I don't disagree with). Linking there from
the release notes entry would require some rewriting to make it fit; I would
just remove the placeholder question for this one.
cheers ./daniel