For installation instructions see the Section called Installing Tcl-8.4.4 in Chapter 5.
Tcl (8.4.4):
http://download.sourceforge.net/tcl/
ftp://download.sourceforge.net/pub/sourceforge/tcl/
(Last checked against version 8.4.4.)
The Tcl package contains the Tool Command Language.
Tcl installs the following files:
tclsh
libtcl8.4.so
(Not checked yet.)