It's not easy to understand what you want.

 
use strict;
use warnings;

my ($test,$test2,$test3);       # parens needed for my(LIST)

print "$test\n"; 
## print nothing

if(not defined $test){
    $test3 = "GOOD";            # no my, no private but upper scope
    print "$test3\n"
} 
## print GOOD 

print "$test\n"; 
## print nothing


if (not defined $test2) {
    print "$test3\n";           # print $test3 from upper scope
}
## print GOOD. GOOD is defined on first "if" function.
[download]

RESULT:

Use of uninitialized value $test in concatenation (.) or string at d:/
+tmp/pm/my.pl line 8.
Use of uninitialized value $test in concatenation (.) or string at d:/
+tmp/pm/my.pl line 15.

GOOD

GOOD
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it's generally a bad idea to print undefined values. I suppose it's a test so I left the warnings in.