Close, but no cigar:

use strict;
use warnings;

sub slice_ref {
   return \@_;
}

my @foo = (1..5);
our @bar; *bar = slice_ref @foo[0..2];
print('foo: ', join(', ', @foo), "\n");
print('bar: ', join(', ', @bar), "\n");

print("\n");

$bar[0] = 'a';
print("After changing bar0:\n");
print('foo: ', join(', ', @foo), "\n");
print('bar: ', join(', ', @bar), "\n");

print("\n");

splice(@bar, 1, 0, 6);
print("After inserting into bar:\n");
print('foo: ', join(', ', @foo), "\n");
print('bar: ', join(', ', @bar), "\n");

print("\n");

$bar[0] = 'b';
print("After changing bar0:\n");
print('foo: ', join(', ', @foo), "\n");
print('bar: ', join(', ', @bar), "\n");

__END__
output
======

foo: 1, 2, 3, 4, 5
bar: 1, 2, 3

After changing bar0:
foo: a, 2, 3, 4, 5
bar: a, 2, 3

After inserting into bar:
foo: a, 2, 3, 4, 5          Want: a, 6, 2, 3, 4, 5
bar: a, 6, 2, 3

After changing bar0:
foo: b, 2, 3, 4, 5          The magic is still there
bar: b, 6, 2, 3                on individual elements.
[download]

By the way, I think you asking for a solution that should not be used in a "heavily-used CPAN module".

Update: Fixed bug in slice_ref, and simplified it. Added comment at bottom.