{
    id      => integer,
    cleared => boolean,
    PR      => [
        { ... },
        ...
        { ... },
    ],
}

##</code><code>##

foreach my $key ( @{ $form->{PR} } ) {

##</code><code>##

         foreach my $var ( keys %elem ) {  
          if ($var->{id} == $form->{"id"}){

##</code><code>##

#!/usr/bin/env perl -l

use strict;
use warnings;

use Data::Dumper;

my $form = {
    id      => 12594,
    cleared => 1,
    PR      => [
        { id => 10368, cleared => 0 },
        { id => 12594, cleared => 0 },
    ],
};

print '*** BEFORE ***';
print Dumper $form;

for my $hash_ref (@{$form->{PR}}) {
    if ($hash_ref->{id} == $form->{id}) {
        $hash_ref->{cleared} = $form->{cleared};
    } 
}

print '*** AFTER ***';
print Dumper $form;

##</code><code>##

*** BEFORE ***
$VAR1 = {
          'cleared' => 1,
          'id' => 12594,
          'PR' => [
                    {
                      'cleared' => 0,
                      'id' => 10368
                    },
                    {
                      'cleared' => 0,
                      'id' => 12594
                    }
                  ]
        };

*** AFTER ***
$VAR1 = {
          'cleared' => 1,
          'id' => 12594,
          'PR' => [
                    {
                      'cleared' => 0,
                      'id' => 10368
                    },
                    {
                      'cleared' => 1,
                      'id' => 12594
                    }
                  ]
        };