The error is not because you are checking an empty array. It comes from Shareable.pm, line 446:

446: return scalar(@{$self->{_data}});
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I'd say your $self->{_data} is not defined at this point. you can just assign an empty list to prevent this:

use IPC::Shareable (':lock');

my @arr;
my %options = ( 
                 create => 'yes',
                 mode => 0644,
                 exclusive => 0,
                 destroy => 'yes'
               );  
my $handle = tie @arr, 'IPC::Shareable', 'dat1', { %options } or die "
+Tie failed.\n";

@arr = (); # INITIALIZE <-----------

if (@arr) {
        print "NOT empty\n";
}
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