use strict;
use warnings;

use feature qw{ say };

my $str = q{1234};
my $ref = \ substr $str, 1, 2;

show();
noRefReset( $_ ) for qw{ a xyz };

$str = q{56789};
show();
noRefReset( $_ ) for qw{ pq ghijkl st };

say q{-} x 18;

$str = q{1234};
$ref = \ substr $str, 1, 2;

show();
refReset( $_ ) for qw{ a xyz };

$str = q{56789};
show();
refReset( $_ ) for qw{ pq ghijkl st };

sub noRefReset
{
    ${ $ref } = shift;
    show();
}

sub refReset
{
    ${ $ref } = shift;
    $ref = \ substr $str, 1, 2;
    show();
}

sub show
{
    printf qq{%-9s - %s\n}, $str, ${ $ref };
}

##</code><code>##

1234      - 23
1a4       - a
1xyz4     - xyz
56789     - 678
5pq9      - pq
5ghijkl9  - ghijkl
5st9      - st
------------------
1234      - 23
1a4       - a4
1xyz      - xy
56789     - 67
5pq89     - pq
5ghijkl89 - gh
5stijkl89 - st