[oak perl] operator question--still confused

[Zed Lopez]

You might like to take another pass through Coping With Scoping.

http://perl.plover.com/FAQs/Namespaces.html

> My problem doesn't involve a loop, merely understanding how "use strict"
> and "my" are supposed to work together.  I may have copied my examples
> incorrectly (sorry!), so they are set forth again here below.  I started
> out with:
> 
> my @numbers = qw(1 4 6);
> $total += $_ for @numbers;
> print $total;

Here, $total is a package variable (implicitly in the main:: package.)
Without using strict, Perl will let you make up new package variables
whenever you feel like it. (This is a feature for one-liners, but not
for anything longer than a few lines, which is why Perl people are so
avid about recommending using strict.)

> which worked, producing a value of "11" to my DOS window.  Then I decided
> to add "use strict;" at the beginning:
> 
> use strict;
> my @numbers = qw(1 4 6);
> $total += $_ for @numbers;
> print $total;
> 
> That gave me errors, asking me to explicitly define $total (I assume with
> "my").  But when I run the following, I get nothing (no return of the value
> and no error messages):

That's a big part of the point of strict: now you can't just make up
package variables on the fly. You can predeclare them with 'use vars',
or you can use lexical variables (declared with 'my') instead.
 
> use strict;
> my @numbers = qw(1 4 6);
> my $total += $_ for @numbers;
> print $total;
> 
> I can't figure out why my first example works, whereas my third doesn't.  I
> figure this is just something simple I'm missing.

The reason this fails _is_ about the for loop, as Steve and I
discussed. $total is undef again after the for loop; you shouldn't use
end-of-line modifiers like 'for' after 'my' statements.

This works:

use strict;
my @numbers = qw(1 4 6);
my $total = 0;
$total += $_ for @numbers;
print $total;