Background
- Three test perl scripts:
-
-
tryStuffAlpha.pm : a small test "hello-world" module that is part of a pair.
tryStuffBeta.pm : a small test "hello-world" module that is part of a pair.
tryStuff_Caller.pl : a script that uses two the test modules.
(NOTE: Alpha and Beta are essentially identical modules, just 'mirror images' of each other with different names.)
- Goals:
-
-
The Alpha and Beta modules need the capability to share one or more scalar
variables with each other.
The Alpha and Beta modules need the capability to share subroutines with each other.
The Caller script needs the capability to access all the common and combined
functionality of the Alpha and Beta modules.
All three scripts are supposed to demonstrate the bare-minimum amount of code
necessary to reach the desired goals in perl.
Original Source Code
The source code of the three scripts is as follows.
tryStuffAlpha
### begin_: tryStuffAlpha.pm
package tryStuffAlpha;
use strict;
use warnings;
use Exporter;
use vars qw(@ISA @EXPORT @EXPORT_OK %EXPORT_TAGS $VERSION);
use vars qw( $PermaLink $OppositePermaLink );
$VERSION = 1.00; # Or higher
@ISA = qw(Exporter);
use tryStuffBeta;
### begin_: init vars
$PermaLink = "PERMALINK-ALPHA\n";
$OppositePermaLink = "AOppositeLink=" .$tryStuffBeta::Permalink."
+\n";
### begin_: subroutines
push @EXPORT_OK, qw( SayHello );
sub SayHello {
my $strOut;
$strOut = "Alpha Says Hello World! \n";
return $strOut;
}###end_sub
push @EXPORT_OK, qw( SayOpposite );
sub SayOpposite {
my $strOut;
$strOut = "Say Opposite Alpha =".tryStuffBeta::SayHello();
return $strOut;
}###end_sub
### begin_: end perl
1;
__END__
tryStuffBeta
### begin_: tryStuffBeta.pm
package tryStuffBeta;
use strict;
use warnings;
use Exporter;
use vars qw(@ISA @EXPORT @EXPORT_OK %EXPORT_TAGS $VERSION);
use vars qw( $PermaLink $OppositePermaLink );
$VERSION = 1.00; # Or higher
@ISA = qw(Exporter);
use tryStuffAlpha;
### begin_: init vars
$PermaLink = "PERMALINK-BETA\n";
$OppositePermaLink = "BOppositeLink=" .$tryStuffAlpha::Permalink.
+"\n";
### begin_: subroutines
push @EXPORT_OK, qw( SayHello );
sub SayHello {
my $strOut;
$strOut = "Beta Says Hello World! \n";
return $strOut;
}###end_sub
push @EXPORT_OK, qw( SayOpposite );
sub SayOpposite {
my $strOut;
$strOut = "Say Opposite Beta =".tryStuffAlpha::SayHello();
return $strOut;
}###end_sub
### begin_: end perl
1;
__END__
tryStuff_Caller
### begin_: tryStuff_Caller.pl
use strict;
use warnings;
use tryStuffAlpha; ### <a href="./tryStuffAlpha.pm" />
use tryStuffBeta; ### <a href="./tryStuffBeta.pm" />
### begin_: main
print "1: ". tryStuffAlpha::SayHello(); ### OK
print "2: ". tryStuffBeta::SayHello(); ### OK
print "3: ". tryStuffAlpha::SayOpposite(); ### OK
print "4: ". tryStuffBeta::SayOpposite(); ### OK
print "5: ". $tryStuffAlpha::PermaLink; ### OK
print "6: ". $tryStuffBeta::PermaLink; ### OK
print "7: ". $tryStuffAlpha::OppositePermaLink; ### FAILS
print "8: ". $tryStuffBeta::OppositePermaLink; ### FAILS
Problem
The three scripts are not behaving as expected and/or desired:
Run Result Alpha : (unexpected1) warns about uninitialized value, apparently b/c it
does not "see" the scalar from the other module.
Run Result Alpha : (unexpected2) warns about redefined subroutines, not sure why.
Run Result Beta : (unexpected3) same problems as Alpha.
Run Result Caller : (expected but not wanted) warns about uninitialized value,
apparently caused by unexpected1.
Run Result Caller : (wanted but not explained) successfully outputs the result
of all subroutines as expected, even though there is the 'redefined' warning
when Alpha and Beta are run individually.
### Run Result Alpha (tryStuffAlpha.pm run all by itself)
Use of uninitialized value ... at tryStuffAlpha.pm line 29.
Use of uninitialized value ... at tryStuffBeta.pm line 29.
Subroutine SayHello redefined ... tryStuffAlpha.pm line 35.
Subroutine SayOpposite redefined ... tryStuffAlpha.pm line 42.
Use of uninitialized value ... tryStuffAlpha.pm line 29.
### Run Result Beta (tryStuffBeta.pm run all by itself)
Use of uninitialized value ... at tryStuffBeta.pm line 29.
Use of uninitialized value ... at tryStuffAlpha.pm line 29.
Subroutine SayHello redefined ... tryStuffBeta.pm line 35.
Subroutine SayOpposite redefined ... tryStuffBeta.pm line 42.
Use of uninitialized value ... tryStuffBeta.pm line 29.
### Run Result Caller (tryStuff_Caller.pm run all by itself)
Use of uninitialized value in concatenation (.) or string at tryStuffB
+eta.pm line 29.
Use of uninitialized value in concatenation (.) or string at tryStuffA
+lpha.pm line 29.
1: Alpha Says Hello World!
2: Beta Says Hello World!
3: Say Opposite Alpha =Beta Says Hello World!
4: Say Opposite Beta =Alpha Says Hello World!
5: PERMALINK-ALPHA
6: PERMALINK-BETA
7: AOppositeLink=
8: BOppositeLink=
Questions
The main question is what is the proper syntax to get the two modules Alpha and Beta to share their scalar variable with each other? What is the reason for the subroutine 'redefined' warnings? What is the way to make all the 'redefined' warnings go away when the modules are run separately? This is apparently a very simple problem of variable scope, any clarification on this issue is welcome.
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