The ways in which the components of a program interact with each
other in a concurrent setting can be considerably more complex
than in a sequential setting. The core problem is unrestricted
shared mutable state. An alternative to unrestricted shared
mutable state is to restrict the sharing using Ownership.
Ownership can turn what would have been a race into a
deterministic failure that can be explained to the programmer.
However, Ownership has predominantly taken place in statically
typed languages.

In this paper, we explore retrofitting an existing dynamically
typed programming language with an ownership model based on
regions. Our core aim is to provide safe concurrency, that is, the
ownership model should provide deterministic dynamic failures of
ownership that can be explained to the programmer. We present a
dynamic model of ownership that provides ownership of groups
objects called regions. We provide dynamic enforcement of our
region discipline, which we have implemented in a simple
interpreter that provides a Python-like syntax and semantics, and
report on our first steps into integrating it into an existing
language, Python.