use strict;
use warnings;
use Data::Dump qw (pp);

my $accounts = [
    {
           'date' => '1980-03-05',
           'year' => '2019',
           'acc' => '44443',
         },
    {
           'date' => '1999-06-19',
           'year' => '2017',
           'acc' => '54321',
         },
    {
           'date' => '1999-09-19',
           'year' => '2099',
           'acc' => '12345',
         },
    ];
    
my $all = [
         {
           'date' => '2000-01-00',
           'year' => '2003',
           'acc' => '4327',
         },
         
         {
           'date' => '1987-01-03',
           'year' => '2013',
           'acc' => '89997',
         },
         
         {
           'date' => '1980-04-18',
           'year' => '2016',
           'acc' => '239876A',
         }, 
         
         {
           'date' => '1999-06-19',
           'year' => '2017',
           'acc' => '54321',
         }
        ]; 

# add all hashes from $accounts to $all if
# the acc == 44443

foreach my $href (@$accounts)
{
     push @$all, $href if $href->{acc} == 44443;
} 

pp $all;
__END__

[
  { acc => 4327, date => "2000-01-00", year => 2003 },
  { acc => 89997, date => "1987-01-03", year => 2013 },
  { acc => "239876A", date => "1980-04-18", year => 2016 },
  { acc => 54321, date => "1999-06-19", year => 2017 },
  { acc => 44443, date => "1980-03-05", year => 2019 },
]