solr-updateprocessors is a set of python scripts that takes advantage of StatelessScriptUpdateProcessorFactory feature present on Solr 4.0
Right now we have 4 scripts avaliable:
FieldAssigner FieldReplacer FieldMapper FieldLookup
You can find an example on how to configure these script inside solrconfig.xml, please keep in mind that you need jython available on collection libraries path like below:
SOLR_HOME/conf /lib /Lib jython.jar
Note: The Lib folder is where you will place the jython modules takes from its installed.