Several new commands support more introspection and control of the Tcl interpreter:

info functions returns a list of all the math functions currently defined. (TIP #15)
info script now accepts an optional pathname argument. If provided, it becomes the return value for all future invocation of info script for the duration of the session. This can be useful in virtual file system applications.
interp recursionlimit sets and returns the maximum depth for nested Tcl procedure calls and other operations that create Tcl stack frames. (TIP #87)
namespace exists reports whether or not a specified namespace exists.