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Subject: Re: A ghost in the machine?
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From: Eric Howe <eric@pieinsky.ca>
In-Reply-To: <4B4F8C70.6090401@1200group.com>
Date: Thu, 14 Jan 2010 13:42:13 -0800
Cc: users Mod_perl <modperl@perl.apache.org>
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Message-Id: <327435C2-956D-4861-8755-5B29BF2ED817@pieinsky.ca>
References: <4B4F6620.4090900@1200group.com>
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To: Tosh Cooey <tosh@1200group.com>

Hi Tosh,

The function sigil ("&") is an archaic left over from before perl5. =
Calling a function as "&cfg" is the same as saying "&cfg(@_)" and that =
implicit "@_" was probably the source of your problem. A bit more =
information can be found here:

=
http://www.perlfoundation.org/perl5/index.cgi?subroutines_called_with_the_=
ampersand

Executive summary: don't use "&" on a sub unless you need a sub-ref:

	my $x =3D \&cfg;
	$x->();


On 2010-01-14, at 13:28 , Tosh Cooey wrote:

> Ok now I'm really boggled...
>=20
> If I use:
>=20
> my $vars =3D { config =3D> &cfg() };
> instead of:
> my $vars =3D { config =3D> &cfg };
>=20
> Then it works!  So what's the difference between &cfg and &cfg() when =
it comes to mod_perl, or at least ModPerl::Registry?
>=20
> Thank-you all...
>=20
> Tosh
>=20
>=20
> Tosh Cooey wrote:
>> True, good point.  I cleaned up my code and changed some things =
around and I still have the same problem:
>> index.pl
>> ########
>> use MyConfig;
>> use ClientConf;
>> use MyUser;
>> my $vars =3D { config =3D> &cfg };
>> MyConfig.pm
>> ###########
>> package MyConfig;
>> use strict;
>> use Exporter;
>> use vars qw(@ISA @EXPORT);
>> @ISA =3D qw(Exporter);
>> @EXPORT =3D qw(&cfg &user);
>> my %CFG =3D { global vars... };
>> sub cfg {
>>   return ClientConf->new();
>> }
>> sub user {
>>   return MyUser->new();
>> }
>> 1;
>> The function "user" works just fine, it returns the object as =
expected.
>> #### BREAK ####
>> So, while I was testing to make sure everything works exactly as I =
described above I discovered unexpected behaviour.  &cfg is actually:
>> sub cfg {
>>  my ($cfg_var) =3D @_;
>>  if ($cfg_var) {
>>    ...do something...
>>  } else {
>>    return ClientConf->new();
>>  }
>> }
>> &user is exactly as noted above.  When I changed &user and added the =
same $cfg_var and conditional it also did not return what I expected.
>> So basically the problem I'm having is that even though I'm calling =
&cfg without arguments that $cfg_var is evaluating as "TRUE", but only =
under ModPerl::Registry and not under regular unadulterated PERL.
>> As a PERL user for 15 years am I just the biggest newbie ever, or is =
there something obscure going on that I should know about?
>> Thanks for anything!
>> Tosh
>> Ihnen, David wrote:
>>> Global?  There's no need to use a global here.   You only ever =
reference %CFG *in* the package... so just make it package scoped - =
it'll act like a static variable and persist.  (scope it with 'my' and =
remove it from the export)
>>>=20
>>> You can always get the value you want with a call to MyConfig::cfg
>>>=20
>>> David
>>>=20
>>> -----Original Message-----
>>> From: Tosh Cooey [mailto:tosh@1200group.com] Sent: Thursday, January =
14, 2010 10:45 AM
>>> To: modperl@perl.apache.org
>>> Subject: A ghost in the machine?
>>>=20
>>> Hi to everyone!
>>>=20
>>> I'm trying to find out if I'm passing objects properly under =
mod_perl because something is not working as I expect.
>>>=20
>>> index.pl
>>> ########
>>> use MyConfig;
>>> my $vars =3D { config =3D> &cfg };
>>>=20
>>>=20
>>> MyConfig.pm
>>> ###########
>>> package MyConfig;
>>>=20
>>> use strict;
>>> use Exporter;
>>> use vars qw(@ISA @EXPORT %CFG );
>>> use ClientConf;
>>> @ISA =3D qw(Exporter);
>>> @EXPORT =3D qw(%CFG &cfg);
>>>=20
>>> %CFG =3D { global vars... };
>>>=20
>>> sub cfg {
>>>   my $CFG{$clientID} =3D new ClientConf;
>>>   return $CFG{$clientID};
>>> }
>>> 1;
>>>=20
>>>=20
>>> Under normal PERL $vars->{config} is a MyConfig object.  Under =
mod_perl nothing is returned.  Debugging with "print" statements in &cfg =
shows me that "ref $CFG{$clientID}" is ClientConf, the object is there, =
but upon return it just disappears.
>>>=20
>>> I have other functions which "return new MyUser()" and these work =
perfectly, so I'm thinking that the problem lies with the global =
variable "$CFG" and that something which I think should be happening is =
NOT happening.
>>>=20
>>> I'm flummoxed...
>>>=20
>>> Thank-you for any insights!
>>>=20
>>> Tosh
>>>=20
>=20
> --=20
> McIntosh Cooey - Twelve Hundred Group LLC - http://www.1200group.com/


Eric Howe
eric@pieinsky.ca