First, keep in mind that
try { ... } ...
is the same thing as
try sub { ... }, ...
and that's the source of many problems.

$GLOBAL_VARIABLE falls out of scope at the end of the (.pm) file, and before 5.10.0, a reference by an anon sub isn't enough to to keep it alive.

Simplified test case:

use strict;
use warnings;

{
   my $f = 'test';
   my $g = 'test';

   sub f {
      sub { print "f: $f\n" }->();
   }

   sub g {
      $g if 0;
      sub { print "g: $g\n" }->();
   }
}

f();
g();
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>perl589\bin\perl test.pl
Use of uninitialized value in concatenation (.) or string at test.pl l
+ine 9.
f:
g: test

>perl5100\bin\perl test.pl
f: test
g: test
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Note that adding a reference to the captured variable in the named sub — even one that's optimized away — makes it available to the anonymous sub.

A similar problem exists with eval '$s'. While not fixed, a warning was added in 5.10.0.

>perl589\bin\perl -wle"{ my $s='test'; sub f { print 's: ', eval '$s' 
+} } f()"
Use of uninitialized value in print at -e line 1.
s: 

>perl5100\bin\perl -wle"{ my $s='test'; sub f { print 's: ', eval '$s'
+ } } f()"
Variable "$s" is not available at (eval 1) line 2.
Use of uninitialized value in print at -e line 1.
s:
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