From return:

In the absence of an explicit return, a subroutine, eval, or do FILE automatically returns the value of the last expression evaluated.

So, since you do not have an explicit return in test2, your code is equivalent to

sub test2 {
   return test();
}
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and hence the propagation. If you want it evaluated in a certain context, then evaluate it in that context, perhaps as

sub test2 {
   test();
   return;
}
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