1. A method comprising: a code processor pre-processing a set of statements that conform to a computer programming language standard, said set of statements including a first aliasing directive and a second aliasing directive, both of which conform to a syntax defined by the computer programming language standard; wherein said syntax specifies that an aliasing directive includes an alias expression and a substitute expression; wherein the first aliasing directive includes a first alias expression and a first substitute expression and the second aliasing directive includes a second alias expression and a second substitute expression; wherein a semantic specified by said computer programming language standard for an aliasing directive is that instances of an alias expression in the set of statements are replaced with a substitute expression corresponding to the aliasing directive during pre-processing of the set of statements; wherein the second substitute expression specifies a processing directive having a semantic different than any semantic specified by said computer programming language standard for a substitute expression of an aliasing directive; wherein said set of statements does not refer to the second alias expression outside of the second aliasing directive; wherein said code processor pre-processing the set of statements includes: replacing the first alias expression with the first substitute expression; pre-processing the second aliasing directive by generating code to carry out the processing directive specified in the second substitute expression.