1mKEYED LISTS0m
       Extended Tcl defines a special type of list referred to as 4mkeyed24m 4mlists24m.
       These lists provided a structured data type  built  upon  standard  Tcl
       lists.   This provides a functionality similar to 4mstruct24ms in the C pro-
       gramming language.

       A keyed list is a list in which each element contains a key  and  value
       pair.   These  element  pairs are stored as lists themselves, where the
       key is the first element of the list, and the value is the second.  The
       key-value  pairs  are  referred  to as 4mfields24m.  This is an example of a
       keyed list:

                  {{NAME {Frank Zappa}} {JOB {musician and composer}}}

       If the variable 1mperson 22mcontained the above list,  then  1mkeylget  person0m
       1mNAME 22mwould return 1m{Frank Zappa}22m.  Executing the command:

            keylset person ID 106

       would make 1mperson 22mcontain

                  {{ID 106} {NAME {Frank Zappa}} {JOB {musician and composer}}

       Fields  may  contain  subfields;  `.' is the separator character.  Sub-
       fields are actually fields where the value is another keyed list.  Thus
       the  following list has the top level fields 4mID24m and 4mNAME24m, and subfields
       4mNAME.FIRST24m and  4mNAME.LAST24m:

                  {ID 106} {NAME {{FIRST Frank} {LAST Zappa}}}

       There is no limit to the recursive depth of subfields, allowing one  to
       build complex data structures.

       Keyed lists are constructed and accessed via a number of commands.  All
       keyed list management commands take the name of the variable containing
       the  keyed  list as an argument (i.e. passed by reference), rather than
       passing the list directly.
