The trinary is semantically just an if expression though. Perl inherits C's problem that `if` can't be used in an expression context:

  my $x = if ($cond) { 1 } else { 2 };  # Syntax error

Because of this, Perl introduces a second syntax to plug the gap:

  my $x = $cond ? 1 : 2;

That expression is neither obtuse nor hard to read.

Something like the code below is hard to read:

  my $fee =
    $is_member
        ? ($is_student ? $student_member_fee : $member_fee)
        : ($is_student ? $student_fee        : $standard_fee);

It's equivalent to the following code that uses `if`:

  my $fee;
  if ($is_member) {
      if ($is_student) {
          $fee = $student_member_fee;
      }
      else {
          $fee = $member_fee;
      }
  }
  else {
      if ($is_student) {
          $fee = $student_fee;
      }
      else {
          $fee = $standard_fee;
      }
  }

But ideally you would want to write this:

  my $fee =
    if ($is_member) {
        if ($is_student) {
            $student_member_fee
        }
        else {
            $member_fee
        }
    }
    else {
        if ($is_student) {
            $student_fee
        }
        else {
            $standard_fee
        }
    };

Though, of course, perl5 doesn't allow that.