Troubleshooting

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       *** LOAD ERROR ***
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Arcadia require ruby-tk extension     
       and tcl/tk run-time 

Solution:

Linux

(this helped me) sudo apt-get install tcl8.5 tk8.5 rvm install 1.9.2 --enable-pthread or rvm reinstall 1.9.2 --enable-pthread

I not sure on other OS, but you need "activetcl" (activestate.com)

OS X

RVM disables tk/tcl by default, you need to tell ruby (via rvm) you want tk/tcl: rvm install 1.9.2 --enable-shared --enable-pthread --with-tk --with-tcl

Windows install

rvm install 1.9.2 --enable-shared --enable-pthread --with-tk --with-tcl

Notes

ruby with --enable-pthread parametr may work slower than without it for Arcadia better install own ruby version with --enable-pthread