user27: I have been hearing a lot lately about "OP_EVAL", what is it? 
Gavin has mentioned it here: http://sourceforge.net/mailarchive/forum.php?thread_name=201110130938.35014.luke%40dashjr.org&forum_name=bitcoin-development
AFAIK it's what the military does after an operation...

user575: OP_EVAL is a new opcode (operation code) for the Bitcoin block chain scripting language, proposed in this thread.
What this opcode does is take a binary representation of a script from the data supplied for authorizing use of an output, and add the corresponding script to what is being evaluated.
The goal of this is to create Bitcoin addresses which, to use, require an arbitrary verification scheme, without people sending to that address needing to know what the script is.
The "killer app" for this is for people who don't want to lose all their bitcoins if their computer is compromised. They will use addresses where coins can only be spent if signatures from two different keys stored on separate devices are provided. Again, this is transparent to others sending to this person, they only need to know the address and not the details of his desired script.

27: <p>I have been hearing a lot lately about "OP_EVAL", what is it? </p>

<p>Gavin has mentioned it here: <a href="http://sourceforge.net/mailarchive/forum.php?thread_name=201110130938.35014.luke%40dashjr.org&amp;forum_name=bitcoin-development" rel="nofollow">http://sourceforge.net/mailarchive/forum.php?thread_name=201110130938.35014.luke%40dashjr.org&amp;forum_name=bitcoin-development</a></p>

<p>AFAIK it's what the military does after an operation...</p>
 575: <p>OP_EVAL is a new opcode (operation code) for the Bitcoin block chain scripting language, proposed in <a href="https://bitcointalk.org/index.php?topic=46538.0">this thread</a>.</p>

<p>What this opcode does is take a binary representation of a script from the data supplied for authorizing use of an output, and add the corresponding script to what is being evaluated.</p>

<p>The goal of this is to create Bitcoin addresses which, to use, require an arbitrary verification scheme, without people sending to that address needing to know what the script is.</p>

<p>The "killer app" for this is for people who don't want to lose all their bitcoins if their computer is compromised. They will use addresses where coins can only be spent if signatures from two different keys stored on separate devices are provided. Again, this is transparent to others sending to this person, they only need to know the address and not the details of his desired script.</p>
