setpath.pl [ENV_VAR] [:NEWPATH | NEWPATH: | -[-]OLDPATH]

  Default ENV_VAR is PATH
  :NEWPATH appends ":NEWPATH" at end of ENV_VAR
  NEWPATH: prepends "NEWPATH:" at start of ENV_VAR
  -OLDPATH deletes first instance of "OLDPATH" from ENV_VAR
  --OLDPATH deletes all instances of "OLDPATH" from ENV_VAR