some bits of the jpm man page

gistfile1.txt

NVIRONMENT
       JANET_TREE
              A convenient way to set the modpath, binpath, syspath, and
              manpath all at once. This is equivalent to the --tree parameter
              to jpm.

       JANET_PATH
              The location to look for Janet libraries. This is the only
              environment variable Janet needs to find native and source code
              modules. If no JANET_PATH is set, Janet will look in the default
              location set at compile time, which can be determined with (dyn
              :syspath)

       JANET_MODPATH
              The location that jpm will use to install libraries to. Defaults
              to JANET_PATH, but you could set this to a different directory
              if you want to. Doing so would let you import Janet modules on
              the normal system path (JANET_PATH or (dyn :syspath)), but
              install to a different directory. It is also a more reliable way
              to install.  This variable is overwritten by the
              --modpath=/some/path if it is provided.

       JANET_HEADERPATH
              The location that jpm will look for janet header files (janet.h
              and janetconf.h) that are used to build native modules and
              standalone executables. If janet.h and janetconf.h are available
              as default includes on your system, this value is not required.
              If not provided, will default to <jpm script
              location>/../include/janet. The --headerpath=/some/path option
              will override this variable.

       JANET_LIBPATH
              Similar to JANET_HEADERPATH, this path is where jpm will look
              for libjanet.a for creating standalone executables. This does
              not need to be set on a normal install.  If not provided, this
              will default to <jpm script location>/../lib.  The
              --libpath=/some/path option will override this variable.