#Put in file TestA.pm in a root lib directory
package TestA;
my $var="TestA";
1;

#Put in file TestB.pm in a root lib directory
package TestB;
use TestA;
my $var2="TestB";

package TestA;
print "'$var','$var2'";
1;

##</code><code>##

'','TestB'

##</code><code>##

'TestA','TestB'

##</code><code>##

package TestA;
{
  my $var="TestA";
  1;
}

package TestB;
{
  use TestA;
  my $var2="TestB";
}
package TestA;
{
  print "'$var','$var2'";
  1;
}