You get some really frightening errors when you "use warnings" on them as well. Most of your subroutines and/or methods are redefined (an error under "use warnings", quietly ignored with out), but the modules do what you expect them to do (last sub-routine redefined wins).

Uncoupling the mess was fun. (For some slightly tweaked value of fun....)

Yes it is possible, but it is not recommended. I just ran into a problem with a module on CPAN that suffers from a circular dependency that crops up in the strangest ways. It has to do with the fact that it is importing functions in a circular dependancy, which by the way is exactly what you are suffering from. Here is an example:

#!/usr/bin/perl

use Crypt::Random;
use Crypt::Random::Generator;

my $gen = new Crypt::Random::Generator Strength => 0;
print $gen->integer(Upper => 100), $/;
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The above will fail (if you are using version 1.13 of Crypt::Random) with the following error:

Which looks pretty similar to your problem!

The solution is to fully qualify your functions instead of importing them (ie use cspace::chelp in your bspace module).

What can make this really frustrating, is that the module may appear to work correctly in most instances, but if the modules get used in the wrong order, you hit a problem. Check out the following code snippet which also triggers the Crypt::Random circular reference bug.

#!/usr/bin/perl
use Tk;
use Net::SFTP;
my $sftp = Net::SFTP->new('localhost');
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Which spews out the following errors:

"makerandom" is not exported by the Crypt::Random module
 "makerandom_itv" is not exported by the Crypt::Random module
 "makerandom_octet" is not exported by the Crypt::Random module
Can't continue after import errors at /usr/local/share/perl/5.8.2/Cryp
+t/Random/Generator.pm line 12
BEGIN failed--compilation aborted at /usr/local/share/perl/5.8.2/Crypt
+/Random/Generator.pm line 12, <GEN0> line 1.
Compilation failed in require at /usr/local/share/perl/5.8.2/Crypt/Ran
+dom.pm line 18, <GEN0> line 1.
BEGIN failed--compilation aborted at /usr/local/share/perl/5.8.2/Crypt
+/Random.pm line 18, <GEN0> line 1.
Compilation failed in require at ../Crypt-DH-0.03/lib//Crypt/DH.pm lin
+e 6, <GEN0> line 1.
BEGIN failed--compilation aborted at ../Crypt-DH-0.03/lib//Crypt/DH.pm
+ line 6, <GEN0> line 1.
Compilation failed in require at ../Net-SSH-Perl-1.25/lib//Net/SSH/Per
+l/Kex/DH1.pm line 13, <GEN0> line 1.
BEGIN failed--compilation aborted at ../Net-SSH-Perl-1.25/lib//Net/SSH
+/Perl/Kex/DH1.pm line 13, <GEN0> line 1.
Compilation failed in require at ../Net-SSH-Perl-1.25/lib//Net/SSH/Per
+l/Kex.pm line 6, <GEN0> line 1.
BEGIN failed--compilation aborted at ../Net-SSH-Perl-1.25/lib//Net/SSH
+/Perl/Kex.pm line 6, <GEN0> line 1.
Compilation failed in require at ../Net-SSH-Perl-1.25/lib//Net/SSH/Per
+l/SSH2.pm line 6, <GEN0> line 1.
BEGIN failed--compilation aborted at ../Net-SSH-Perl-1.25/lib//Net/SSH
+/Perl/SSH2.pm line 6, <GEN0> line 1.
Compilation failed in require at ../Net-SSH-Perl-1.25/lib//Net/SSH/Per
+l.pm line 51, <GEN0> line 1.
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Not very nice is it... So the moral of the story is, don't use circular references, and if you really have to, fully qualify your functions.

- Cees

In your case, this is what happens:

a.pl line 1 compiled: "use bspace"
bspace line 1 compiled: package bspace;
bspace line 2 compiled: use Exporter;
Exporter.pm compiled
main code of Exporter.pm executed
Exporter::->import called (uselessly)
bspace line 3 compiled: use cspace;
cspace line 1 compiled: package cspace;
cspace line 2 compiled: use Exporter;
Exporter::import called (uselessly)
cspace line 3 compiled: use bspace;
bspace::->import called (but doesn't yet exist since bspace::ISA is no
+t yet set to inherit import() from Exporter, so bgo and bhelp are not
+ imported into cspace)
cspace line 4 compiled but not executed: @ISA = 'Exporter'
cspace line 5 compiled but not executed: @EXPORT = qw(cgo chelp);
cspace line 6 compiled: sub cgo { bhelp(); }
cspace line 7 compiled: sub chelp { print "chelp\n"; }
cspace line 8 compiled but not executed: 1;
cspace lines 4,5,8 executed
cspace::->import called: cgo and chelp are exported into bspace
bspace line 4 compiled but not executed: @ISA = 'Exporter'
bspace line 5 compiled but not executed: @EXPORT = qw(bgo bhelp);
bspace line 6 compiled: sub bgo { chelp(); }
bspace line 7 compiled: sub bhelp { print "bhelp\n"; }
bspace line 8 compiled but not executed: 1;
bspace lines 4,5,8 executed
bspace::->import called: bgo and bhelp are exported into main
a.pl line 2 compiled: use cspace
cspace::->import called: cgo and chelp are exported into main
a.pl line 3 compiled but not executed: bgo()
a.pl line 4 compiled but not executed: cgo()
a.pl line 3 executed: bgo() (imported from bspace)
bspace::bgo calls chelp() (imported from cspace)
cspace::chelp prints "chelp\n"
a.pl line 4 executed: cgo() (imported from cspace)
cspace::cgo calls bhelp() which was not imported from bspace and so do
+esn't exist.
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package bspace;
use strict;
use warnings;
use Exporter (); # () avoids (harmless but) useless call to Exporter::
+import;
BEGIN {
    our @ISA = 'Exporter';
    our @EXPORT = qw(bgo bhelp);
}
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# A.pm
package A;
use strict;
use warnings;
use Exporter ();
BEGIN { our @ISA = 'Exporter'; our @EXPORT = 'foo' }
sub foo { print "foo" }
# and in the same file A.pm
package A::B;
use A;
sub bar { foo() } # without the BEGIN block above, the use A won't hav
+e imported foo into A::B
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Nowadays, it is recommended to import 'import' from Exporter instead of inheriting it, so:

package bspace;
use strict;
use warnings;
use Exporter 'import';
BEGIN {
    our @EXPORT = qw(bgo bhelp);
}
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