concat [ arg arg ... ]
This command treats each argument as a list and concatenates them into a single list. It also eliminates leading and trailing spaces in the args and adds a single separator space between args. It permits any number of arguments. For example, the command
concat a b {c d e} {f {g h}}
will return
a b c d e f {g h}
as its result.
If no args are supplied, the result is an empty string.