Additionally, you can only have one package-global variable of the same type and the same name in the same package, so the second import will override the first.

use dir_one::my_package qw(%my_hash);
BEGIN {
 # force this to run before the "use" below
 print "%s\n", Dumper(\%my_hash);
}
use dir_two::my_package qw(%my_hash);

print "%s\n", Dumper(\%my_hash);
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update: also, print() doesn't do what you seem to think it does. See print and printf/sprintf. in this case,

print Dumper(\%my_hash);
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update 2: almut reminded me that since you specified "%my_hash" in @EXPORT (and not @EXPORT_OK) it will get exported automatically, so you don't need to specify it again when importing. You still need to use "use" or call import yourself, though. That would make the final code something like this:

use dir_one::my_package;
BEGIN {
 # force this to run before the "use" below
 print Dumper(\%my_hash);
}
use dir_two::my_package;

print Dumper(\%my_hash);
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Thank you very much for your help. It was a typo in my code that I had written "print" instead of "printf". I succeeded in reading the packages in the current directory where my script is.

However, I am running this case on a Cygwin platform and Perl interpreter cannot find the packages residing other than current directories although I declare them even within @INC. The directory of the said Perl script resides in

/home/UTKU/devel/my_script
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The said packages are located in

/home/UTKU/devel/my_script/dir_one/my_package.pm
/home/UTKU/devel/my_script/dir_two/my_package.pm
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Now the script tries following:

#!/usr/bin/perl -w

BEGIN { push @INC, "/home/UTKU/devel/my_script" }
use Data::Dumper;
use dir_two::my_package;

print Dumper(\%my_hash);
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Perl interpreter says me that my_hash is used only once, ie. it seems that the package has not been bound:

$ ./my_script.pl
Name "main::my_hash" used only once: possible typo at ./my_script.pl l
+ine 9.
$VAR1 = {};
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I know, interpreter takes the current directory into @INC but it also does not work. Can't I define packages with relative paths? The content of the package in /home/UTKU/devel/my_script/dir_two/my_package.pm is like in my first posting:

##! /usr/local/bin/perl
package my_package;

require(Exporter);
@ISA = qw(Exporter);
@EXPORT = qw(
             %my_hash
          );

%my_hash = (
...
);
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Is there any mechanism to switch on verbose messages during compilation/elaboration/linkage time of the interpreter to see what it is doing with the packages?

I think your problem is that you haven't put the right package names in the .pm files, i.e.

  dir_one/my_package.pm  --> package dir_one::my_package;
  dir_two/my_package.pm  --> package dir_two::my_package;
                                     ^^^^^^^
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BTW, if the hash is the only thing in the packages, you can just leave off any package declarations entirely. Then you also don't need the Exporter stuff, as the hash will end up in the main:: namespace anyway... (However, don't do that, if there's other code in the modules!)