ふと気がついたのですが、Tcl/Tk が入っていない環境でも、tkutil は
install されるようです。これは意図された挙動でしょうか?

% cvs -d :pserver:anonymous / cvs.ruby-lang.org:/src co ruby
...
% cd ruby 
% autoconf 
% ./configure --prefix=/tmp/r     
...
% make                       
...
compiling tcltklib
compiling tk
make[1]: Entering directory `/tmp/r/ruby/ext/tk'
gcc -fPIC -g -O2  -I. -I../.. -I../../. -I../.././ext/tk   -c tkutil.c
gcc -shared  -L'../..' -o ../../.ext/i686-linux/tkutil.so tkutil.o  -ldl -lcrypt -lm   -lc
cp ../.././ext/tk/lib/multi-tk.rb ../../.ext
cp ../.././ext/tk/lib/remote-tk.rb ../../.ext
cp ../.././ext/tk/lib/tk.rb ../../.ext
...
cp ../.././ext/tk/lib/tkextlib/winico/setup.rb ../../.ext/tkextlib/winico
cp ../.././ext/tk/lib/tkextlib/winico/winico.rb ../../.ext/tkextlib/winico
cp ../.././ext/tk/lib/tkextlib/SUPPORT_STATUS ../../.ext/tkextlib
make[1]: Leaving directory `/tmp/r/ruby/ext/tk'
...
% make install
...
./miniruby ./ext/extmk.rb --dest-dir="" --make="make" --mflags="" --make-flags="" --extout=".ext" --extension  --extstatic  -- install
cp -r ./.ext/. /tmp/r/lib/ruby/1.9
...
% ls /tmp/r/lib/ruby/1.9
English.rb    find.rb         open-uri.rb        ripper.rb      tkdialog.rb
Env.rb        forwardable.rb  open3.rb           rss            tkentry.rb
abbrev.rb     ftools.rb       openssl            rubyunit.rb    tkextlib
base64.rb     generator.rb    openssl.rb         runit          tkfont.rb
benchmark.rb  getoptlong.rb   optparse           scanf.rb       tkmacpkg.rb
bigdecimal    getopts.rb      optparse.rb        set.rb         tkmenubar.rb
cgi           gserver.rb      ostruct.rb         sha1.rb        tkmngfocus.rb
cgi-lib.rb    i686-linux      parsearg.rb        shell          tkpalette.rb
cgi.rb        importenv.rb    parsedate.rb       shell.rb       tkscrollbox.rb
complex.rb    io              pathname.rb        shellwords.rb  tktext.rb
csv.rb        ipaddr.rb       ping.rb            singleton.rb   tkvirtevent.rb
date          irb             pp.rb              soap           tkwinpkg.rb
date.rb       irb.rb          prettyprint.rb     sync.rb        tmpdir.rb
date2.rb      jcode.rb        profile.rb         tempfile.rb    tracer.rb
debug.rb      kconv.rb        profiler.rb        test           tsort.rb
delegate.rb   logger.rb       pstore.rb          thread.rb      un.rb
digest        mailread.rb     racc               thwait.rb      uri
dl            mathn.rb        rational.rb        time.rb        uri.rb
drb           matrix.rb       rdoc               timeout.rb     weakref.rb
drb.rb        md5.rb          readbytes.rb       tk             webrick
e2mmap.rb     mkmf.rb         remote-tk.rb       tk.rb          webrick.rb
erb.rb        monitor.rb      resolv-replace.rb  tkafter.rb     wsdl
eregex.rb     multi-tk.rb     resolv.rb          tkbgerror.rb   xmlrpc
expect.rb     mutex_m.rb      rexml              tkcanvas.rb    xsd
fileutils.rb  net             rinda              tkclass.rb     yaml
finalize.rb   observer.rb     ripper             tkconsole.rb   yaml.rb
% ./ruby -rtkutil -e ''
/tmp/r/lib/ruby/1.9/i686-linux/tkutil.so: No such file to load -- tcltklib (LoadError)

すくなくとも tkutil は install されたにもかかわらず require に失敗する
ようです。
-- 
[田中 哲][たなか あきら][Tanaka Akira]