Have you tried:

use strict;
use warnings;
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I see require Exporter; line is missed in your example.

Update: Here's the working code:

package XYZ;
use strict;
use warnings;
require Exporter;
our @ISA       = qw(Exporter);
our @EXPORT_OK = qw(%Hash1);
our ( %Hash1, %Hash2 );

sub populateHashRoutine {
    %Hash1 = ( a => 1, b => 2, );
    %Hash2 = ( c => 3, d => 4, );
}

1;
[download]

use strict;
use warnings;
use Data::Dumper;
use XYZ qw(%Hash1);

XYZ::populateHashRoutine;
warn Dumper \%Hash1, \%XYZ::Hash2;
__END__
$VAR1 = {
          'a' => 1,
          'b' => 2
        };
$VAR2 = {
          'c' => 3,
          'd' => 4
        };
[download]