fish: Invalid index value
echo "$foo[d]"
           ^
fish: Invalid index value
echo $foo[d]
          ^
fish: Invalid index value
echo ()[d]
        ^

####################
# Percent self

####################
# Catch your breath
fish: $) is not a valid variable in fish.
echo $$paren
      ^

####################
# Test tilde expansion

####################
# Test path variables