I'd suggest using Exporter:

# Module1.pm
package Module1;
our %variable;
use base 'Exporter';
our @EXPORT_OK = qw(%variable);

%variable = ( foo => "foo" );

# Module2.pm
package Module2;
use Module1 qw(%variable);

print $variable{foo};
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However, if you plan to use this variable to exchange data between the modules, I'd suggest using subroutine arguments instead.