[Proj] concatenate EPSG codes in proj4?

[Duffy, Garret]

Hi,

Does proj4 support concatenation of EPSG codes?  e.g. I would like to
concatenate any projection with EPSG operation 9621.  I would ideally
like to do this in QGIS.

If not, does anyone have any advice how to do this?

Thanks,

Garret