The values of all arguments are concatenated with space separators
and the resulting list is evaluated as a Tcl
script.
The main usage of this command is to enforce another parsing
level or metacalling.
Note that list values may have to be passed using the list
or concat command:
% set a {a b c d}
a b c d
% eval llength $a
wrong # args: should be "llength list"
% eval llength [list $a]
4