This is basically a simple way to format things side by side, in arrangements such as this:
HPANE basically takes its sub elements and format them horizontally, and taking into account max/min constraint parameters which the sub elements may specify. See section on HPANE for more.
Here's layout showing the combined use of a number of features to achieve multiple columns...
Similar effects can be achieved with the table tags. But HPANE is more of a geometry managing device than for tabulation. HPANE is also not a replacement for a real multiple-columns text flow mechanism, thou it can be roughly used as such. It's included because it's simple and useful for many things.
Relic columning formatter. Untested.