Alternation Syntax

Alternation syntax similar to that used in Unix shells may also be used:

%{%{Foo}:-bar}

This code returns the value of %{Foo}, if it has a value. Otherwise, it returns a literal string bar.

%{%{Foo}:-%{Bar}}

This code returns the value of %{Foo}, if it has a value. Otherwise, it returns the expansion of %{Bar}.

These conditional expansions can be nested to almost any depth, such as with %{%{One}:-%{%{Two}:-%{Three}}}.

%{%{Stripped-User-Name}:-%{User-Name}}
%{%{Framed-IP-Address}:-<none>}