A doctor, an engineer, and a fungal taxonomist arrived at The Pearly Gates of Heaven.
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."