A  '(B)*' template can obviate some split-ing and join-ing (although the marginal array-length checking is no longer present):

c:\@Work\Perl\monks>perl -le
"use warnings;
 use strict;
 ;;
 use Test::More 'no_plan';
 use Test::NoWarnings;
 ;;
 my @TESTS = (
   'degenerate case',
   [ [], [], [], ],
   'simple cases',
   [ [ 0 ], [ 0 ], [ 0 ], ],
   [ [ 0 ], [ 1 ], [ 1 ], ],
   [ [ 1 ], [ 0 ], [ 1 ], ],
   [ [ 1 ], [ 1 ], [ 1 ], ],
   'complex cases',
   [ [ 0, 1, 0, 1, ],
     [ 0, 0, 1, 1, ],
     [ 0, 1, 1, 1, ],
     ],
   [ [ 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, ],
     [ 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, ],
     [ 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, ],
     ],
   );
 ;;
 VECTOR:
 for my $ar_vector (@TESTS) {
   if (not ref $ar_vector) {
     note $ar_vector;
     next VECTOR;
     }
   ;;
   my ($ar_x, $ar_y, $ar_expected) = @$ar_vector;
   ;;
   use constant TEMPLATE => '(B)*';
   my $v1 = pack TEMPLATE, @$ar_x;
   my $v2 = pack TEMPLATE, @$ar_y;
   my @got = unpack TEMPLATE, $v1 | $v2;
   is_deeply \@got, $ar_expected, qq{(@got)};
   }
 ;;
 done_testing;
 ;;
 exit;
"
# degenerate case
ok 1 - ()
# simple cases
ok 2 - (0)
ok 3 - (1)
ok 4 - (1)
ok 5 - (1)
# complex cases
ok 6 - (0 1 1 1)
ok 7 - (0 1 1 1 0 1 1 1 1 1 1 1)
1..7
ok 8 - no warnings
1..8
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Update: Oops... Originally posted with template '(a)*' (which also works, but produces longer intermediate strings) instead of '(B)*': Fixed.