[mod_python] ./configure fails on freebsd 6.0

Hi there. I'm trying to compile mod_python on a freebsd 6.0 box, but 
configure fails. It seems to be a shell script problem.

./configure --with-apxs=/usr/local/apache2/bin/apxs
... ... ...
checking linker flags used to link Python...
checking where Python include files are... -I/usr/local/include/python2.4
./configure: line 3427: syntax error near unexpected token `('
./configure: line 3427: `  as_lineno_3=`(expr $as_lineno_1 + 1) 
2>/dev/null`'

Any suggestions? Thanks.