use IPC::Shareable ':lock';
[...]
no warnings 'untie';
my $knot;
my $glue = "SHMEMGLUE";
eval { $knot = tie %tie, 'IPC::Shareable', $appdata{$glue}, { create => 0, mode => 0666, size => $appdata{SHMEMSIZE},
                                                             exclusive => 0, destroy => 0 };
        };
unless ($@) {
   $knot->remove;
   untie %tie;
   undef $knot;
}
$knot = tie %tie, 'IPC::Shareable', $appdata{$glue}, { create => 1, mode => 0666, size => $appdata{SHMEMSIZE},
                                                          exclusive => 0, destroy => 0 };
untie %tie;