Well, you've got two problems that I see already. First,

my $reg = \INIT();
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That takes a reference to the result obtained from invoking that subroutine right there, not a reference to the subroutine itself. If you want a chance of that working, you'll want my $reg = \&subroutinename instead. But, keep reading...

Second, the name "INIT" is reserved. From perldoc perlmod:

       "INIT" blocks are run just before the Perl runtime begins execu
+tion, in
       "first in, first out" (FIFO) order. For example, the code gener
+ators
       documented in perlcc make use of "INIT" blocks to initialize an
+d
       resolve pointers to XSUBs.
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