info complete command
Returns 1 if command is a complete Tcl command in the sense of having no unclosed quotes, braces, brackets or array element names, If the command doesn't appear to be complete then 0 is returned. This command is typically used in line-oriented input environments to allow users to type in commands that span multiple lines; if the command isn't complete, the script can delay evaluating it until additional lines have been typed to complete the command.
RS: Could it be that info complete can be used generally to check whether a string can be parsed as a list? I used to use
expr {![catch {llength $x}]}for that purpose...
See also: