Apache::Watchdog::RunAway 2.x works with both mod_perl generations. If you have both installed you need to decide which mod_perl generation to build it for. To build against mod_perl 1.0, run: *** mod_perl 1.0 *** % perl Makefile.PL MOD_PERL=1 -httpd /path/to/apache/bin/httpd % make % make test % make install replace /path/to/apache/bin/httpd with a path to your apache 1.3 httpd server, which was built with mod_perl 1.0. An alternative way to tell Makefile.PL that you want mod_perl 1.0 is server, which was built with mod_perl 1.0 to use the MOD_PERL environment variable: % MOD_PERL=1 perl Makefile.PL -httpd /path/to/apache/bin/httpd % make % make test % make install *** mod_perl 2.0 *** You can't use this module with threaded mpms. Since when a process is killed all threads in it will be killed. % perl Makefile.PL MOD_PERL=2 -httpd /path/to/apache2/bin/httpd % make % make test % make install replace /path/to/apache/bin/httpd with a path to your apache 2.0 httpd server, which was built with mod_perl 2.0. An alternative way to tell Makefile.PL that you want mod_perl 2.0 is server, which was built with mod_perl 2.0 to use the MOD_PERL environment variable: % MOD_PERL=2 perl Makefile.PL -httpd /path/to/apache2/bin/httpd % make % make test % make install