Hi!
The INSTALL file lists Kamailio's dependencies at the beginning (which is really great, thanks!).
libpcre is needed when building with
make group_include="standard mysql" all
which is encouraged in the INSTALL file. In Debian Lenny, you need to install libpcre3-dev.
This dependency should be included in the INSTALL file.
I encountered this in version 3.0.
Best regards,
Victor