When a plug-in step finishes processing, its default post-processing element is executed. The post-processing element is defined in the plug-in's XML definition, see Creating Plug-ins.
You can override the default behavior by entering your own script into the step's Post Processing Script field. A post-processing script can contain any valid JavaScript code. Although not required, it's recommended that scripts be wrapped in a CDATA element.
See the <post-processing> Element for more information.