For hash tables you have two options: the dictionary[1] or the Tcl array[2], which is more or less like an Awk array.

Can you give me an example of powerful string handling?

string[3] for the usual string manipulations.

subst[4] when you want weird string substitutions (works like a template).

regsub[5] and regexp[6] for regular expressions.

[1] http://www.tcl.tk/man/tcl/TclCmd/dict.htm

[2] http://www.tcl.tk/man/tcl/TclCmd/array.htm

[3] http://www.tcl.tk/man/tcl/TclCmd/string.htm

[4] http://www.tcl.tk/man/tcl/TclCmd/subst.htm

[5] http://www.tcl.tk/man/tcl/TclCmd/regsub.htm

[6] http://www.tcl.tk/man/tcl/TclCmd/regexp.htm