Do you want to add the numbers with the same keys?

#!/usr/bin/perl
use warnings;
use strict;

use Data::Dumper;

my %parent = (
    'file3232.ext' => {
        e => 0,
        k => '0.0031',
        i => '26.9',
        j => '33.0',
    }
);

my %returned = (
    'file3232.ext'  => {
        e => 0,
        k => '0.1040',
        i => '26.7',
        j => '14.6',
    }
);

for my $file (keys %returned) {
    for my $dataset (keys %{ $returned{$file} }) {
        $parent{$file}{$dataset} += $returned{$file}{$dataset};
    }
}

print Dumper \%parent;
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Using Hash::Merge is the following: retrieve the most similar predefined behaviour, modify it to your needs (e.g. define the addition of scalar values) and use it to merge the hashes:

use Hash::Merge qw{ merge };

my $behavior = Hash::Merge::get_behavior_spec('STORAGE_PRECEDENT');
$behavior->{SCALAR}{SCALAR} = sub { $_[0] + $_[1] };
Hash::Merge::add_behavior_spec($behavior);

%parent = %{ merge(\%parent, \%returned) };

print Dumper \%parent;
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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