src/main/java/com/bazaarvoice/jless/parser/Parser.java
Rule Parameter() {
        return Sequence(
                Variable(), push(new VariableDefinitionNode(match())), peek().setVisible(!isParserTranslationEnabled()), Ws0(),
                ':', Ws0(),
                ExpressionPhrase(), peek(1).addChild(new ExpressionGroupNode(pop()))
        );
    }
Rule Parameter() {
        return Sequence(
                Variable(), push(new VariableDefinitionNode(match())), peek().setVisible(!isParserTranslationEnabled()), Ws0(),
                ':', Ws0(),
                ExpressionPhrase(), peek(1).addChild(new ExpressionGroupNode(pop()))
        );
    }
Variable Ws0 ':' Ws0 ExpressionPhrase