%then keyword (SDL script)
The %then keyword is used within an if...then...else statement. The %then keyword specifies a set of statements to run if the condition is satisfied.
* 
The optional %else keyword specifies a set of statements to run if the condition is not satisfied.
Syntax
%if <condition> %then
<set of statements for when condition is satisfied>
[%else
<set of statements for when condition is not satisfied>]
%endif
In this example the value of the Return Type property is evaluated. If the value of the Return Type property is void, 'return;' is generated, if the value is not void, 'return ReturnValue;' is generated.
%if %custom "Return Type" == "void" %then
"return;"
%else
"return ReturnValue;"
%endif