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

I'm trying to export scalars from a module as below. MODULE: 
use Exporter;
use vars qw(@ISA @EXPORT $VERSION);

@ISA = qw(Exporter);
@EXPORT = qw(Execute GetValue $PACKAGE_REQUEST_ID $BUGNUMBER $KBARTICL
+E $DISTMETHOD $MINSP $MAXSP $ISNONINSTALLINGPKG $JOBBRANCHNAME $HOTPA
+TCHBINARIES $BINARIESAFFECTED $BUGTITLE);
$VERSION = '1.00';


my($PACKAGE_REQUEST_ID, $BUGNUMBER, $KBARTICLE, $DISTMETHOD, $MINSP, $
+MAXSP, $ISNONINSTALLINGPKG, $JOBBRANCHNAME, $HOTPATCHBINARIES, $BINAR
+IESAFFECTED, $BUGTITLE);


BEGIN {

print "Begin has begun\n";

    $PACKAGE_REQUEST_ID = "PackageRequestID";
    $BUGNUMBER = "bugnumber";
    $KBARTICLE = "kbarticle";
    $DISTMETHOD = "distmethod";
    $MINSP = "minsp";
    $MAXSP = "maxsp";
    $ISNONINSTALLINGPKG = "isnoninstallingpkg";
    $JOBBRANCHNAME = "jobbranchname";
    $HOTPATCHBINARIES = "hotpathbinaries";
    $BINARIESAFFECTED = "binariesaffected";
    $BUGTITLE = "bugtitle";

    print "PRI is $PACKAGE_REQUEST_ID\n";

}

[download]
I believe this successfully exports the scalars because the interpreter doesn't complain when I access them from a pl file where use strict is enabled. However, when I try to access these variables, they are set to no value: 

    print "WHAT VALUE? $PACKAGE_REQUEST_ID" . "\n";

[download]
prints "WHAT VALUE?\n". What am I doing wrong?

Replies are listed 'Best First'.
Re: Exporting scalars from a module
by leriksen (Curate) on May 03, 2004 at 07:21 UTC
    OK, what you think you are doing is not what you are actually doing...

    The problem is the my(...). This declares a whole bunch of lexically scoped variables, which are completely different to the symbols in the @EXPORT array. Things in the @EXPORT... structures are things in the packages symbol table - and lexically scoped variables are most definitely not in the symbol table.

    I'll say again - the things in the my() are not the same as the things in the @EXPORT array. This is the crux of your issue.

    The quickest solution is to change the my to our (if your perl has this new-ish keyword) or change the my to use vars qw(...) and remove the commas in the list.

    package thingy;

use warnings;
use strict;

use Exporter;
use vars qw(@ISA @EXPORT $VERSION);

use vars qw($PACKAGE_REQUEST_ID $BUGNUMBER $KBARTICLE $DISTMETHOD $MIN
+SP $MAXSP $ISNONINSTALLINGPKG $JOBBRANCHNAME $HOTPATCHBINARIES $BINAR
+IESAFFECTED $BUGTITLE);


@ISA = qw(Exporter);
@EXPORT = qw(Execute GetValue $PACKAGE_REQUEST_ID $BUGNUMBER $KBARTICL
+E $DISTMETHOD $MINSP $MAXSP $ISNONINSTALLINGPKG $JOBBRANCHNAME $HOTPA
+TCHBINARIES $BINARIESAFFECTED $BUGTITLE);
$VERSION = '1.00';

...

    [download]
    The longer solution is to read every article in Tutorials on variables. Only then may you claim true mastery.

    +++++++++++++++++
    #!/usr/bin/perl
    use warnings;use strict;use brain;

[reply]
[d/l]
      Rule #1 of programming: Repetition is evil. 
      my @xvars;
BEGIN { @xvars = qw($PACKAGE_REQUEST_ID $BUGNUMBER $KBARTICLE $DISTMET
+HOD $MINSP $MAXSP $ISNONINSTALLINGPKG $JOBBRANCHNAME $HOTPATCHBINARIE
+S $BINARIESAFFECTED $BUGTITLE) }

use vars ( qw(@ISA @EXPORT $VERSION), @xvars );

require Exporter;
@ISA = qw(Exporter);
@EXPORT = ( qw(Execute GetValue), @xvars );

      [download]

          -- Chip Salzenberg, Free-Floating Agent of Chaos

[reply]
[d/l]
        How can I enable use strict and not use my to declare the variables? (The version of perl we use does not support the our keyword): 

        package ExitCode;


my @varsToExport = qw(%exitCodes $EXIT_SUCCESS $EXIT_GENERAL_FAILURE $
+EXIT_CHANGELIST_CONSUMED $EXIT_FUTURE_CHANGELIST);

require Exporter;
use vars (qw(@ISA @EXPORT), @varsToExport);
@ISA = qw(Exporter);
@EXPORT = qw(@varsToExport);

%exitCodes;


# Define exit codes
$EXIT_SUCCESS = 0;

        [download]
[reply]
[d/l]

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