Allow the use of HISADDR, MYADDR and INTERFACE as words embedded in the args of a "shell" or "!bg" command, and only accept upper case versions.
Allow the use of HISADDR, MYADDR and INTERFACE as words
embedded in the args of a "shell" or "!bg" command, and
only accept upper case versions.

We can now do:
  ! sh -c "ifconfig INTERFACE >/tmp/myfile"

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase