use strict;
use warnings;
use 5.010;

use Data::Dump qw(dump dd ddx);
use Test::More;

sub match {    # $pat, $str_ref
    warn "\nmatch", dump @_;
    my $pat     = $_[0];
    my $str_ref = $_[1];
    my @res;
    say STDERR '$str_ref before loop: ', dump $str_ref;
    while ( my $rv = $$str_ref =~ m{$pat}g ) {
        say STDERR 'in loop: ', dump $str_ref, $rv, @{^CAPTURE};
        push @res, @{^CAPTURE};
    }
    say STDERR 'match: ', ( dump @res ), "\n";
    return @res;
}

sub spliT {    # $pat, $str_ref
    warn "\nspliT", dump @_;
    my @rv = split $_[0], ${ $_[1] };
    say STDERR 'split: ', ( dump @rv ), "\n";
    return @rv;
}

$_ = 'ERROR?';
/(.+)/;        # set $1

my $match_OK = [ ':', ':' ];
my $split_OK = [ "a", ":", "b", ":", "c" ];

is_deeply [ match( qr{(:)}, \'a:b:c' ) ], [ ':', ':' ], q{\'a:b:c'};

my $dollar1_ref;
{
    my $str = 'a:b:c';
    $_ = $str;
    /(.+)/;
    $dollar1_ref = \$1;
    warn "\n\$dollar1_ref: ", dump $dollar1_ref;

    is_deeply [ match( qr{(:)}, $dollar1_ref ) ], $match_OK, q{$dollar1_ref};
    warn "NOK because \$\$dollar1_ref is changed by m{}\n";

    warn "\n\$dollar1_ref: ", dump $dollar1_ref;
    is_deeply [ spliT( qr{(:)}, $dollar1_ref ) ], $split_OK,
      q{spliT( qr{(:)}, $dollar1_ref)};

    warn "\n\$dollar1_ref: ", dump $dollar1_ref;
    warn "\n ===== leave scope";
}

warn "\n\$dollar1_ref: ", dump $dollar1_ref;

# $dollar1_ref =  \undef
# is_deeply [ match( qr{(:)}, $dollar1_ref ) ], $match_OK, q{$dollar1_ref};
# is_deeply [ spliT( qr{(:)}, $dollar1_ref ) ], $split_OK,
#  q{spliT( qr{(:)}, $dollar1_ref};

done_testing();

__DATA__
output:

match(qr/(:)/, \"a:b:c") at pm_5.pl line 17.
$str_ref before loop: \"a:b:c"
in loop: (\"a:b:c", 1, ":")
in loop: (\"a:b:c", 1, ":")
match: (":", ":")

ok 1 - \'a:b:c'

$dollar1_ref: \"a:b:c" at pm_5.pl line 51.

match(qr/(:)/, \"a:b:c") at pm_5.pl line 17.
$str_ref before loop: \"a:b:c"
in loop: (\":", 1, ":")
match: ":"

not ok 2 - $dollar1_ref
#   Failed test '$dollar1_ref'
#   at pm_5.pl line 53.
#     Structures begin differing at:
#          $got->[1] = Does not exist
#     $expected->[1] = ':'
NOK because $$dollar1_ref is changed by m{}

$dollar1_ref: \"a:b:c" at pm_5.pl line 56.

spliT(qr/(:)/, \"a:b:c") at pm_5.pl line 31.
split: ("a", ":", "b", ":", "c")

ok 3 - spliT( qr{(:)}, $dollar1_ref)

$dollar1_ref: \"a:b:c" at pm_5.pl line 60.

 ===== leave scope at pm_5.pl line 61.

$dollar1_ref: \"ERROR?" at pm_5.pl line 64.
1..3
# Looks like you failed 1 test of 3.