OGNL has a simplified lambda-expression syntax, which lets you write simple functions. It is not a full-blown lambda calculus, because there are no closures---all variables in OGNL have global scope and extent.

For example, here is an OGNL expression that declares a recursive factorial function, and then calls it:

#fact = :[#this<=1? 1 : #this*#fact(#this-1)], #fact(30H)

The lambda expression is everything inside the brackets. The #this variable holds the argument to the expression, which is initially 30H, and is then one less for each successive call to the expression.

OGNL treats lambda expressions as constants. The value of a lambda expression is the AST that OGNL uses as the parsed form of the contained expression.