Geo::Coordinates::OSGB(3pm) on Linux
The text 4971f242daff, as Debian 13 (Trixie), Debian 12 (Bookworm) shipped it. The page shows this text now.
Convert coordinates between Lat/Lon and the British National Grid An implementation of co-ordinate conversion for England, Wales, and Scotland based on formulae and data published by the Ordnance Survey of Great Britain.