% concat a b {c d e} {f {g h}} a b c d e f {g h}
it will also concatenate things that are not lists, as can be seen from this session:
% concat " a b {c " d " e} f" a b {c d e} f
Note also that the concatenation does not remove spaces from the middle of values, as can be seen here:
% concat "a b c" { d e f } a b c d e f
(i.e., there are three spaces between each of the a, the b and the c).
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.
Licensed under Tcl/Tk terms
https://www.tcl.tk/man/tcl/TclCmd/concat.htm