Ah, the joys of debugging global variables! Iron-clad employment insurance!! You'll be working on this until the end of time — or until the company goes under, not unlikely if they've got a lot of code like this.

Here's one approach, not necessarily the best: track down the package the hash lives in (assuming it's a package global):

c:\@Work\Perl\monks>perl -wMstrict -le
"no strict qw(refs vars);
 no warnings;
 ;;
 package Foo;
 %CONTACTS = ('hello' => 'sailor');
 ;;
 package Bar;
 $ZOT{'autovivified'} = 'bam';
 ;;
 package main;
 ;;
 my $rx_pkg = qr{ \A (?: [[:alpha:]] [[:alnum:]]* ::)+ \z }xms;
 ;;
 print qq{'$_'} for
   grep m{ $rx_pkg }xms,
   keys %main::
   ;
 print '';
 ;;
 print qq{'$_' has 'CONTACTS'} for
   grep exists ${$_}{CONTACTS},
   grep m{ $rx_pkg }xms,
   keys %main::
   ;
 print '';
 ;;
 print qq{'$_' has 'ZOT'} for
   grep exists ${$_}{ZOT},
   grep m{ $rx_pkg }xms,
   keys %main::
   ;
 print '';
 ;;
 print $Foo::CONTACTS{'hello'};
 print $Bar::ZOT{'autovivified'};
"
'version::'
'utf8::'
're::'
'CORE::'
'DynaLoader::'
'mro::'
'strict::'
'Win32CORE::'
'Bar::'
'Regexp::'
'UNIVERSAL::'
'Foo::'
'main::'
'Carp::'
'Win32::'
'PerlIO::'
'IO::'
'Exporter::'
'Internals::'
'warnings::'
'DB::'

'Foo::' has 'CONTACTS'

'Bar::' has 'ZOT'

sailor
bam
[download]

• This code only runs if some strictures are disabled (no strict qw(refs vars);) — and it doesn't hurt to disable warnings also — you may have to turn all these off locally;
• This shows the package the hash lives in, but how it got there is another story;
• The example code shows hash definition in Foo, autovivification in Bar. For your purposes, they amount to the same thing.

Updates:

1. Added
       no strict qw(refs vars);
       no warnings;
   statements to example code.
2. Check out Packages and Symbol Tables in perlmod.
3. Actually, on re-reading the docs, I think
       my $rx_pkg = qr{ \A (?: [[:alpha:]_] \w* ::)+ \z }xms;
   would be a better definition of the package name regex.