class Sass::Tree::VariableNode

def _perform(environment)
  return [] if @guarded && !environment.var(@name).nil?
  val = @expr.perform(environment)
  if @expr.context == :equals && val.is_a?(Sass::Script::String)
    val = Sass::Script::String.new(val.value)
  end
  environment.set_var(@name, val)
  []
end