Re: proposed addition to perlvar

On Tue, Jun 8, 2010 at 16:29, Abigail <[email protected]> wrote:
> On Tue, Jun 08, 2010 at 12:22:38PM -0400, Chas. Owens wrote:
>> Due to some [confusion a new user had][1] finding the documentation
>> for what $# does in $#foo, I suggest we add a small note to perlvar to
>> point people in the right direction (patch inlined).
>>
>> diff --git a/pod/perlvar.pod b/pod/perlvar.pod
>> index ed90610..359dd62 100644
>> --- a/pod/perlvar.pod
>> +++ b/pod/perlvar.pod
>> @@ -879,6 +879,17 @@ as described below.
>>
>>  Also see L<Error Indicators>.
>>
>> +=item $#
>> +
>> +C<$#> is not a variable; it is a sigil like C<@> that can be prepended
>> +on the name of an array to get the index of the last item in that array.
>> +
>> +    my @a            = ("a", "b", "c");
>> +    my $last_index   = $#a;     # $last_index is 2
>> +    my $last_element = $a[$#a]; # $last_element is "c"
>> +
>> +Also see L<perldata>.
>> +
>
>
> But $# *is* a variable. Until recently (5.8.9), it was even a variable
> with magic, and hence documented in perlvar. Nowadays, it's a somewhat
> normal variable:
>
>  $ perl -wE '$# = 3; say $#'
>  $# is no longer supported at -e line 1.
>  3
>  $
>
> Perhaps it's best to re-add $# to perlvar, and write something like:
>
>  =item $#
>
>  C<$#> used to be a variable that could be used to format printed number.
>  After a deprecation cycle, its magic was removed in 5.10.
>
>  C<$#> is also used as sigil, which, when prepended on the name of an
>  array gives the index of the last element in that array.
>
>      my @a            = ("a", "b", "c");
>      my $last_index   = $#a;     # $last_index is 2
>      my $last_element = $a[$#a]; # $last_element is "c"
>
>  Also see L<perldata>.
>
>
> I had not realized the $# entry was complete removed from perlvar. I don't
> think it's a bad thing to have a little perl history in the docs. And since
> its use does trigger a warning, it *is* in a way a special variable. And hence
> belongs in perlvar.
>
>
> Abigail
>

How about:

=item $#

C<$#> used to be a variable that could be used to format printed number.
After a deprecation cycle, its magic was removed in 5.10 and using it
now triggers a severe warning: C<$# is no longer supported>.

C<$#> is also used as sigil, which, when prepended on the name of an
array gives the index of the last element in that array.

    my @a            = ("a", "b", "c");
    my $last_index   = $#a;     # $last_index is 2
    my $last_element = $a[$#a]; # $last_element is "c"

Also see L<perldata>.


If we are going to add $# back, should we add back $* as well?

=item $*

C<$*> used to be a variable that enabled multiline matching.
After a deprecated cycle, its magic was removed in 5.10.
Using it now triggers a severe warning: C<$* is no longer
supported>.  Use the C</s> and C</m> regexp modifiers
instead.

Also see L<perlre>.

-- 
Chas. Owens
wonkden.net
The most important skill a programmer can have is the ability to read.