"A doctor, an engineer, and" joke

A doctor, an engineer, and a
fungal taxonomist arrived at The Pearly Gates.
The doctor said how he'd
healed the sick, helped the lame; but he was
a sinner and was sent
to Hell.
The engineer told how he'd built homes for the
homeless, etc.; but he
messed up the environment, so he was sent to
Hell.
The fungal taxonomist was frightened by all this, but as soon as
he
mentioned his occupation, God said "You've already been thru
Hell,
Welcome to Heaven."