Learning Perl, 5th Edition

The return Operator

The return operator immediately returns a value from a subroutine:

my @names = qw/ fred barney betty dino wilma pebbles bamm-bamm /;
my $result = &which_element_is("dino", @names);

sub which_element_is {
  my($what, @array) = @_;
  foreach (0..$#array) {  # indices of @array's elements
    if ($what eq $array[$_]) {
      return $_;         # return early once found
    }
  }
  −1;                    # element not found (return is optional here)
}

This subroutine is being used to find the index of "dino" in the array @names. First, the my declaration names the parameters: there’s $what, which is what we’re searching for, and @array, an array of values to search within. That’s a copy of the array @names, in this case. The foreach loop steps through the indices of @array (the first index is 0, and the last one is $#array, as you saw in Chapter 3).

Each time through the foreach loop, we check to see whether the string in $what is equal^[*] to the element from @array at the current index. If it’s equal, we return that index at once. This is the most common use of the keyword return in Perl—to return a value immediately, without executing the rest of the subroutine.

But what if we never found that element? In that case, the author of this subroutine has chosen to return −1 as a “value not found” code. It would be more Perlish, perhaps, to return undef in that case, but this programmer used −1. Saying return −1 on that last line would be correct, but the word return isn’t really needed.

Some programmers like to use return ...