

     KEYED LISTS
          Extended Tcl defines a special type of list referred to as
          keyed lists.  These lists provided a structured data type
          built upon standard Tcl lists.  This provides a
          functionality similar to structs in the C programming
          language.  A keyed list is a list in which each element is a
          key and value pair field.  These elements are actually lists
          themselves, were the key is the first element of the list,
          and the value is the second.  The key-value pairs are
          refered to as fields.  This is an example of a keyed list:

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

          By convention, `.' is a field name separator, allowing
          nesting of fields, even though keyed list are only one level
          deep.  Currently none of the commands explictly function on
          nested field names, but they may in a future release, so `.'
          should not be used for other than a field separator in a
          name.  For example:

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

          All key list functions take the name of the variable
          containing the keyed list as an argument (i.e. passed by
          reference) rather than the value.
