-If the <tt>configure</tt> command cannot locate Tcl and Tk in your standard
-locations for libraries searched by your C compiler it will guess
-that the libraries are located in <tt>/usr/local/lib</tt> and that
-the header files are located in <tt>/usr/local/include</tt>.
-If this is incorrect you will have to modify the <tt>Makefile</tt> yourself.
+The <tt>configure</tt> command tries to locate the file <tt/tclConfig.sh/
+which should be generated by Tcl's installation script. Configure
+looks for your Tcl shell in order to locate this file. For example
+if <tt/tclsh/ is located in <tt>/home/joe/bin</tt>, configure will
+assume that <tt>tclConfig.sh</tt> is installed in <tt>/home/joe/lib</tt>,
+in which case the prefix is <tt>/home/joe</tt>. If you have
+more than one Tcl version installed on your system, or if configure
+cannot find the Tcl shell in your path, you can specify the prefix
+by adding <tt>--prefix=</tt>prefix to the configure command, i.e.
+<tscreen><verb>
+$ ./configure --prefix=/home/joe
+</verb></tscreen>
+
+The prefix is also used to determine where <sf/IrTcl/ is installed.
+The <sf/IrTcl/ executables are installed in prefix/bin and libraries
+and support files are installed in prefix/irtcl.