String map help

I believe they are functionally equivalent. But, the second command is expressly setting the correct type for the mapping parameter. Most likely is that TCL is seeing you are passing in a string in the first command and trying to coerce it to an list of search/replace strings which that parameter is supposed to represent. Since you have a space in that string, it's convering it to the equivalent of 2.

In an example with the TCL interpreter (tclsh), here's something similar:

% set s 123456
123456
% string map {1 a} $s
a23456
% string map "1 a" $s
a23456

-Joe