What is the recommended way of concatenation of strings?
Answer
Tcl does concatenation of strings as a fundamental operation; there's not really even syntax for it because you just write the strings next to each other (or the variable substitutions that produce them).
set combined $a$b
If you're doing concatenation of a variable's contents with a literal string, it can be helpful to put braces around the variable name or the whole thing in double quotes. Or both:
set combined "$a${b}c d"
Finally, if you're adding a string onto the end of a variable, use the append command; it's faster because it uses an intelligent memory management pattern behind the scenes.
append combined $e $f $g
# Which is the same as this:
set combined "$combined$e$f$g"