...
$accounts = grep { !/44443/ } @$accounts;
# It should have this in account:<br>

print Dumper $accounts;
$VAR2 = {
           'date' => '1999-06-19',
           'year' => '2017',
           'acc' => '54321',
         };
         
# Want to add the array $accounts to $all once I have the data I need in $accounts array.
...
my $main_account = "12345";
@{ $all->{ $main_account }};

# Add $accounts to $all if array $accounts had the data I need only.
@{ $all->{ $main_account }}; = $accounts;

print Dumper $all;

$VAR1 = {
           'date' => '2000-01-00',
           'year' => '2003',
           'acc' => '4327',
         };
$VAR2 = {
           'date' => '1987-01-03',
           'year' => '2013',
           'acc' => '89997',
         };
$VAR3= {
           'date' => '1980-04-18',
           'year' => '2016',
           'acc' => '239876A',
         };          
$VAR4 = {
           'date' => '1999-06-19',
           'year' => '2017',
           'acc' => '54321',
         };