fish is v2.2.0-2.2

Define a function that works as a command alias, for example:

function grep
  /usr/bin/grep -i -E --color=auto $argv
end

Then run an openssl command that requires reading a password, and pipe the
output through the function:

openssl enc -aes256 -in encrypted -d | grep abc

Immediately results in openssl error "bad password read", and no attempt is
made to read a password.

If the pipe destination was not a function, openssl has no trouble reading the
password:
openssl enc -aes256 -in pass -d | /usr/bin/grep -i -E --color=auto abc