class Sass::Environment

so that they can be made available to {Sass::Script::Functions}.
Environment also keeps track of the {Engine} options
but new variables are defined locally.
so it has access to variables defined in enclosing scopes,
The new environment refers to the environment in the upper scope,
This allows variables to be lexically scoped.
A new environment is created for each level of Sass nesting.
This keeps track of variable, mixin, and function definitions.
The lexical environment for SassScript.