As nouns the difference between hern and pern
is that
hern is (obsolete|or|dialectal) corner or
hern can be (dialectal|or|poetic) heron while
pern is part of a spinning wheel, a conical spool onto which the thread is wound from the spindle or
pern can be a honey buzzard;
pernis apivorus .
As a pronoun hern
is hers; her own.
As a verb pern is
to take profit of; to make profitable.