A subroutine is always part of some expression. The value of the subroutine invocation is called the *return value*. The return value of a subroutine is the value of the *return* statement or of the last expression evaluated in the subroutine.

For example, let's define this subroutine:

sub sum_of_a_and_b { return $a + $b; }

The last expression evaluated in the body of this subroutine (in fact, the only expression evaluated) is the sum of `$a`

and `$b`

, so the sum of `$a`

and `$b`

will be the return value. Here's that in action:

$a = 3; $b = 4; $c = sum_of_a_and_b(); # $c gets 7 $d = 3*sum_of_a_and_b(); # $d gets 21

A subroutine can also return a list of values when evaluated in a list context. Consider this subroutine and invocation:

sub list_of_a_and_b { return ($a,$b); } $a = 5; $b = 6; @c = list_of_a_and_b(); # @c gets (5,6)

The last expression evaluated really means the last expression evaluated, rather than the last expression defined in the body of the subroutine. For example, this subroutine returns `$a`

if `$a`

`>`

`0`

; otherwise, it returns `$b`

:

sub gimme_a_or_b { if ($a > 0) { print "choosing a ($a)\n"; return $a; } else { print "choosing b ($b)\n"; return $b; } }

These examples are all rather trivial. It gets better when we can pass values that are different for each invocation into a subroutine, instead of having to rely on global variables. In fact, this discussion is coming right up.