Tcl contains some semantic equivalences such as:
$ ~~ [set]
[] ~~ [eval]
"" ~~ [subst]
Where ~~ can be read as is semantically equivalent to
Add more if you find them. The hunt is on.
escargo 7/7/7 - Are you looking for examples how these are not equivalent?
For example, I seem to recall that [eval] does a round of substitution before evaluating its input. (Logically, it would seem to be necessary for [] !~ [eval], otherwise eval is just taking up space.)
And subst takes arguments that allow limitations on the substitutions.