Using Arrays in Logstash

Hi All,
I've got a field which represents a list of destinations, represented by a decimal values
I now need to "translate" each of those destinations to their IP equivalent.
I'm trying to use the following code:

ruby {	init => " 	'[DestDec][]'
		code => " DestDec.each{|x| event['[DestIP][x]'] = event['[DestDec][x]'].to_i].pack('N').unpack('C4').join('.')}"

but I'm getting a Ruby exception occurred: uninitialized constant LogStash::Filters::Ruby::DestDec.

what am I doing wrong?
how do I initialize an array?

What is [DestDec][] and [DestIP][] supposed to mean? It doesn't look like valid Ruby code. What does the original event look like and what do you want to transform it to?