| name | the name of the variable to define | Yes | 
    | value | the new value the variable must take | Yes | 
    | override | true if the previous value (if any) of the variable should overriden, false otherwise | No, defaults to true | 
    | ifset | the variable will be set only if the provided 'ifset' variable is already set (Since 2.4) | No | 
    | unlessset | the variable will not be set unless the provided 'unlessset' variable is set (Since 2.4) | No |