Every conditional block begins with an 
if statement and ends with
                and 
endif statement. Within the 
if statement,
                the control expression inside the parentheses is evaluated first. If the value of
                the control expression is zero or 
false and there is an
                    
else statement, then the statement following the
                    
else statement is executed. If there is no
                    
else, the statement following 
endif is
                executed. If the value of the control expression evaluates to any other value, the
                expression is 
true and the statement following the
                    
if is executed. A multiway decision can be expressed as a
                series of 
elseif statements within the control block. Such a
                control decision block looks like
                this:
{if (expr)}
     templex statements1
{elseif(expr)}
     templex statements2
{elseif(expr)
     templex statements3
{else}
     templex statements4
{endif}