The l3experimental packages are a collection of experimental
implementations for aspects of the LaTeX3 kernel, dealing with
higher-level ideas such as the Designer Interface. Some of them
work as stand alone packages, providing new functionality, and
can be used on top of LaTeX2e with no changes to the existing
kernel. The present release includes: l3draw, a code-level
interface for constructing drawings; l3str, support for string
manipulation; xcoffins, which allows the alignment of boxes
using a series of 'handle' positions, supplementing the simple
TeX reference point; xgalley, which controls boxes receiving
text for typesetting.

Homepage:
https://ctan.org/pkg/l3experimental
