I tried that, and I still get the same thing. I think the issue is that it's getting into the subroutine, but erroring out in that subroutine, so it never exits that subroutine, making it a moot point what it returns. This is what I did:

Updated with debug statements:

        print "DEBUG: get_host: " . GetHosts($_, \%data) . "\n";
        print "DEBUG: get_new_fw: " . GetNewFWRules($_, \%data) . "\n"
+;
        my %do_for = (
            get_hosts => GetHosts($_, \%data),
            get_new_fw_rules => GetNewFWRules($_, \%data),
        );
        #print "while\n";
        print "DEBUG: do_for: " . $do_for{$what_to_do} . "\n";
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and added return values to the subroutine:

sub GetHosts {
....
    return 1;
}
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I get the same error and output as before, and none of the new debug statements are printed.