[stack] Concatenative scripting language in Bitcoin

I thought this might interest some concatenative people. The virtual
currency Bitcoin has a stack based scripting language built in for
creating transactions. The intent was to allow extending the types of
transactions (other than just "send money to address X") via scripting
to allow various types of contracts, escrow, etc. Some information on
the language is here: https://en.bitcoin.it/wiki/Script

Recently there has been discussion on adding an 'eval' feature that
allows popping a program off the stack and executing it. This is
similar to concatenative languages like Joy. the general proposal is
here: https://en.bitcoin.it/wiki/BIP_0012

This has raised some discussion on the bitcoin development mailing
list about whether this gives the scripting language too much power.
Can it now be used to create loops or otherwise work around some of
the existing languages constraints and subvert the bitcoin transaction
system. Discussion is on this mailing list post:
http://sourceforge.net/mailarchive/message.php?msg_id=28602033

This is an interesting example of stack based languages in real world systems.

Chris.
-- 
http://www.bluishcoder.co.nz