Listing 2 Multiple compiler versions

>> mpich1: "    MPICH1 MPI libraries (including f90 bindings)" <<

mpich1 <= commercial :   PATH += /opt/mpich1/bin,
                        MANPATH += /opt/mpich1/man,
                        LD_LIBRARY_PATH += /opt/mpich1/lib;

>> mpich2: "    MPICH2 MPI libraries" <<

mpich2:                 PATH += /opt/mpich2/bin,
                        MANPATH += /opt/mpich2/man,
                        LD_LIBRARY_PATH += /opt/mpich2/lib;

>> gcc335: "   GCC 3.3.5 (older libraries than system default 3.4.3)" <<

gcc335:                 PATH += /opt/gcc335/bin,
                        MANPATH += /opt/gcc335/man,
                        LD_LIBRARY_PATH += /opt/gcc335/lib32;

>> gcc343: "   GCC 3.4.3 (Current default system compiler)" <<

gcc343: PATH += /usr/x86_64-pc-linux-gnu/gcc-bin/3.4.3/,
        MANPATH += /usr/share/gcc-data/x86_64-pc-linux-gnu/3.4.3/man,
        LD_LIBRARY_PATH += /usr/lib/gcc/x86_64-pc-linux-gnu/3.4.3;

>> gcc4: "     GCC 4.0 (beta version, use at own risk. Provides F95)" <<

gcc4:   PATH += /usr/x86_64-pc-linux-gnu/gcc-bin/4.0.0-beta20050402,
        MANPATH += /usr/share/gcc-data/x86_64-pc-linux-gnu/ \
          4.0.0-beta20050402/man,
        LD_LIBRARY_PATH += /usr/lib/gcc/x86_64-pc-linux-gnu/ \
          4.0.0-beta20050402;

>> commercial: "Commercial compilers" <<

commercial:              PATH += /opt/commercial/bin,
                        MANPATH += /opt/commercial/man,
                        LD_LIBRARY_PATH += \
                          /opt/commercial/lib/2.1:/opt/gcc335/lib32;