scancontext ?option?
              This  command  manages  file scan contexts.  A scan
              context is a collection of regular expressions  and
              commands  to  execute  when that regular expression
              matches a line of the file.   A  context  may  also
              have  a single default match, to be applied against
              lines that do not match any of the regular  expres-
              sions.   Multiple  scan contexts may be defined and
              they may be reused on multiple files.  A scan  con-
              text  is identified by a context handle.  The scan-
              context command takes the following forms:

       scancontext create
              Create a new scan context.  The  scanmatch  command
              is  used to define patterns in the context.  A con-
              texthandle is returned, which  the  Tcl  programmer
              uses  to refer to the newly created scan context in
              calls to the Tcl file scanning commands.

       scancontext delete contexthandle
              Delete  the  scan  context  identified  by  contex-
              thandle,  and  free all of the match statements and
              compiled regular expressions  associated  with  the
              specified context.

              This command is provided by Extended Tcl.