Misc

variable-exists(red)    // checks for $red
mixin-exists(red-text)  // checks for @mixin red-text
function-exists(redify)

global-variable-exists(red)

selector-append('.menu', 'li', 'a')   // .menu li a
selector-nest('.menu', '&:hover li')  // .menu:hover li
selector-extend(...)
selector-parse(...)
selector-replace(...)
selector-unify(...)