PL/PGSQL stat failed on file '$libdir/plpgsql'

Hi,

Since Linux Mandrake 9.1 came out, I have this problem with pl/pgsql:

[root(at)localhost jo]# su postgres
bash-2.05b$ createdb test
CREATE DATABASE
bash-2.05b$ createlang plpgsql test
ERROR: stat failed on file '$libdir/plpgsql': No such file or directory
createlang: language installation failed
bash-2.05b$
bash-2.05b$

Does anybody know what is going on?

Following a hint found with google:

bash-2.05b$ pg_config --pkglibdir
bash: pg_config: command not found
bash-2.05b$ exit
exit
[root(at)localhost jo]# pg_config --pkglibdir
bash: pg_config: command not found

[root(at)localhost jo]# echo $libdir

[root(at)localhost jo]#

What should this variable contain?

[root(at)localhost jo]# cd /usr/local
[root(at)localhost local]# ls
bin/ doc/ etc/ games/ include/ lib/ libexec/ pgsql/ sbin/ share/
src/ vortaro/
[root(at)localhost local]# cd pgsql
[root(at)localhost pgsql]# ls
bin/ doc/ include/ lib/ man/ share/
[root(at)localhost pgsql]# cd lib
[root(at)localhost lib]# ls
ascii_and_mic.so* latin2_and_win1250.so* libpq.a
utf8_and_big5.so* utf8_and_gb18030.so* utf8_and_tcvn.so*
cyrillic_and_mic.so* latin_and_mic.so* libpq.so@
utf8_and_cyrillic.so* utf8_and_gbk.so* utf8_and_uhc.so*
euc_cn_and_mic.so* libecpg.a libpq.so.3@
utf8_and_euc_cn.so* utf8_and_iso8859_1.so* utf8_and_win1250.so*
euc_jp_and_sjis.so* libecpg.so@ libpq.so.3.0*
utf8_and_euc_jp.so* utf8_and_iso8859.so* utf8_and_win1256.so*
euc_kr_and_mic.so* libecpg.so.3@ plpgsql.so*
utf8_and_euc_kr.so* utf8_and_johab.so* utf8_and_win874.so*
euc_tw_and_big5.so* libecpg.so.3.4.1* utf8_and_ascii.so*
utf8_and_euc_tw.so* utf8_and_sjis.so*
[root(at)localhost lib]#

Is everything present?

[root(at)localhost lib]# su postgres
bash-2.05b$ echo $libdir

bash-2.05b$ export libdir=/usr/local/pgsql/lib
bash-2.05b$ echo $libdir
/usr/local/pgsql/lib
bash-2.05b$ createlang plpgsql test
ERROR: stat failed on file '$libdir/plpgsql': No such file or directory
createlang: language installation failed
bash-2.05b$

I'm stuck, hope anybody can help me out

Many thanks,

Jo