Dynamic Job References are more efficient because they allow you to assign a reference, instead of implicitly defining each specific Job name. Dynamic Job References may be substituted anywhere in the matrix file where explicit Job names are required (except for Import Arrays).

Note: Dynamic Job References begin with: @

Here are a listing of the dynamic layer types available throughout the matrix file.
Dynamic Job References	Description
@active	Use the Active Job.
@current	Use the Active Job. (Same as "active")
@topcell	Use the Top Cell (if hierarchy).
@first	First Job that was imported
@last	Last Job that was imported
@1	First Job that was imported
@3	Third Job that was imported
@ -1	Last Job minus 1 (i.e second to last)
@ -3	Last Job minus 3 (i.e fourth to last)