join - Create a string by joining together list elements

       The list argument must be a valid Tcl list.  This command returns the string formed by joining all of the
       elements  of  list  together  with  joinString separating each adjacent pair of elements.  The joinString
       argument defaults to a space character.

       Making a comma-separated list:

              set data {1 2 3 4 5}
              join $data ", "
                   →1,2,3,4,5

       Using join to flatten a list by a single level:

              set data {1 {2 3} 4 {5 {6 7} 8}}
              join $data
                   →12345{67}8

       element, join, list, separator

Tcl                                                                                                   join(3tcl)

       join - Create a string by joining together list elements

list(3tcl), lappend(3tcl), split(3tcl)

joinlist ?joinString?
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