help with Exporter

why_bird has asked for the wisdom of the Perl Monks concerning the following question:

Hey all, I'm having some difficulty with Exporter. I would prefer to use the Readonly module instead, but I don't have admin permissions which I would need to install it at work.

I want to declare some constants in a header-type file, and then use them in lots of other scripts. So far, I have in 'definitions.pm':

#! /usr/bin/perl

package definitions;

require Exporter;
@ISA= qw(Exporter);
use strict;
use warnings;

######################################
## definitions so that if constants ##
## change or are wrong, they can be ##
## easily updated                   ##

@EXPORT=qw(CONST CONST2);

use constant CONST => 2;
use constant CONST2 => 3;

1;
[download]

That was basically copied from the Exporter documentation. In 'temp.pl' i have:

#! /usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

use definitions;

print Dumper CONST;
print Dumper "CONST";
print CONST

exit 0;
[download]

so firstly, when I call temp.pl I get: "Global symbol "@EXPORT" requires explicit package name at definitions.pm line 16" so I try adding 'my' before @EXPORT: "Bareword "CONST" not allowed while "strict subs" in use at ./temp.pl line 10." so I try 'our' and get the same error, then i try 'use Exporter' rather than 'require': same results as above.

If I just run 'definitions.pm' using my @EXPORT, it will at least print '2'. but that's as far as I can get. bah. any suggestions?

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Replies are listed 'Best First'.
Re: help with Exporter by ikegami (Patriarch) on Feb 28, 2008 at 09:11 UTC
`our @EXPORT` or `use vars qw( @EXPORT );`. Same for `@ISA`. By the way, no special privileges are needed to install modules. They can be installed in a directory where you have permission.	[reply] [d/l] [select]
Re^2: help with Exporter by why_bird (Pilgrim) on Feb 28, 2008 at 09:42 UTC
I can't un-tar the module I want. It says I don't have the right permissions. Thanks though, I'll have another go.	[reply]
Re: help with Exporter by moritz (Cardinal) on Feb 28, 2008 at 09:15 UTC
BTW the same applies for `@ISA` - it should be declared with our. But since that is after you `use strict;`, perl won't complain. Another way is thise: `use base Exporter`, or don't inherit from Exporter at all: `use Exporter qw(import);` [download]	[reply] [d/l] [select]
Re^2: help with Exporter by why_bird (Pilgrim) on Feb 28, 2008 at 09:51 UTC
Ok, I tried this: snippet: `... ## easily updated ## our @ISA= qw(Exporter); our @EXPORT=qw($NPR_TO_DAC $NPR_TO_ADC); use constant CONST => 2; ...` [download] but I still got Bareword "CONST" not allowed while "strict subs" in use at ./temp.pl line 10. So I removed @ISA, and tried use base 'Exporter' instead: `#! /usr/bin/perl package definitions; require Exporter; use base 'Exporter'; use strict; use warnings; ################# ## definitions ## our @EXPORT=qw($NPR_TO_DAC $NPR_TO_ADC); use constant CONST => 2; use constant CONST2 => 3; print CONST; 1;` [download] this gave the same Bareword error. I think half the problem is that I don't really understand what Exporter is doing or how it works... I have read the documentation, but I'm still somewhat new at this..! Thankyou for your help so far---any further tips?	[reply] [d/l] [select]
Re^3: help with Exporter by moritz (Cardinal) on Feb 28, 2008 at 10:03 UTC
I tried your second snippet (copied and pasted to a new script), and it runs! I have a perl 5.8.8, what's your perl version? And are you sure you tried exactly the same script as you posted here?	[reply]
Re: help with Exporter by ferreira (Chaplain) on Feb 28, 2008 at 23:00 UTC
Others have already given complete answers to your question, but I would like to point out that the documentation of the latest release (5.62) of Exporter contains an extra section named Good Practices. There you find a subsection Declaring @EXPORT_OK and Friends that contains exactly the kind of explanation to solve your doubts.	[reply]


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