Are you trying to do something like this?

#!/usr/bin/perl

# https://perlmonks.org/?node_id=1228412

use strict;
use warnings;

my $one =
  {
  data  => {
             dir1 => {
                       fileA => { pid => { 61781 => 1 }, total => 13 }
+,
                       fileB => { pid => { 61799 => 1 }, total => 12 }
+,
                     },
             dir2 => {
                       fileA => { pid => { 61439 => 1 }, total => 5 },
                       fileC => { pid => { 12345 => 1 }, total => 10 }
+,
                     },
           },
  total => { fileA => 18, fileB => 12, fileC => 10 },
  };

my $two =
  {
  data  => {
             dir3 => {
                       fileA => { pid => { 616161 => 1 }, total => 6 }
+,
                       fileD => { pid => { 54321 => 1 }, total => 12 }
+,
                     },
             dir4 => {
                       fileA => { pid => { 1718 => 1 }, total => 2 },
                       fileE => { pid => { 15151 => 1 }, total => 3 },
                     },
           },
  total => { fileA => 8, fileD => 12, fileE => 3 },
  };

sub combinemanyhashes
  {
  my $newhash = 
    {
    data => { map %{ $_->{data} // {} }, @_ },
    total => do
      {
      my %total;
      for my $href ( @_ )
        {
        $total{$_} += $href->{total}{$_} for keys %{ $href->{total} //
+ {} };
        }
      \%total;
      }
    };
  return $newhash;
  }

my $totalhashref = {};

$totalhashref = combinemanyhashes( $totalhashref, $one, $two );

use Data::Dump 'dd'; dd $totalhashref;
[download]

Not quite but thank you for the reply. I have created the following sub:


    my ($name,$dirs,$final_href) = @_;
    my %data;
    foreach my $dir (@{$dirs})
    {

        decode($dir."/".$name,%data); # will change name
        my $final_href = 
        (
            data => { ( %{$final_href->{data} },%{ $data{data} } ) },
            total => do
            {
                my %total;
                for my $href ( $final_href->{total}, $data{total} ) {
                 $total{$_} += $href->{total}{$_} for keys %{ $href->{
+total} };
                }
            \%total;
            }
        );
    }
[download]

But it won't work because when I pass $final_href to this sub, it is empty, so it will fail "Can't use an undefined value as a HASH reference"
. I tried to add:


$files_href->{data} = ();
$files_href->{total} = ();
[download]

But it also does not work. it wants a real hash (because we do dereferencing with %{$final_href->{data}).
Any ideas how to solve it?

Try and see what happens