multiple ENVironments

[rhymes against]

Good morning,

I need the following environment variables set to compile the courier
mta and authentication components, and unset to compile the dragonfly
os.  Is there a convenient way to set this up so I don't need to
remember to do and undo this every 6-8 months?

LDFLAGS=-L/usr/pkg/lib
CPPFLAGS=-I/usr/pkg/include
LD_LIBRARY_PATH=/usr/pkg/lib:/usr/local/lib:/usr/lib

cheers.