I am unsure about what you intend. Some code below.
I highly recommend against using experimental features except for "fun code".

#!/usr/bin/perl


use strict;
use warnings;

my $VAR1 = [
          '11',
          '14'
        ];
        
#create a hash...
my %owner_grouprights = map{$_=>1}@$VAR1;

if ($owner_grouprights{'11'})
{
   print "test3-> 11 exists as a groupright\n";
}


# you say: "the big deal -- if it only would work" WHAT??
### what do you expect???

if (grep{/4|5|6|7|8|9|10|11|12/} keys (%owner_grouprights))
{
   print "test2->some number exists as a groupright\n";  #11 exists
}


# with loop
my $testarrorig = '4|5|6|7|8|9|10|11|12';
my @testarr = split( /\|/, $testarrorig );

foreach my $tst ( @testarr ) 
{
  if (exists $owner_grouprights{$tst})
  {
     print "$tst hit!\n";
  }
}
__END__
test3-> 11 exists as a groupright
test2->some number exists as a groupright
11 hit!
[download]

Update: I am very circumspect about smart match. Sometimes this critter is too smart! And produces unexpected results. I don't see the need for it in the above code.