$VAR1 = {
          '10' => 'Test1,Test2,Test3,Test4,Test5,Test6',
          '20' => 'Test4'
        };
[download]

$VAR1 = {
          '10' => 'Test1,Test3,Test5,Test6'
        };
[download]

#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;

my %new_reports = (
             10 => 'Test1,Test2,Test3,Test4,Test5,Test6',
             20 => 'Test4'
        );

print Dumper(\%new_reports);

my @key_to_search = qw(10 20);
my @element_to_delete = qw(Test2 Test4);

foreach (@key_to_search) {
            if($new_reports{$_}) {
                my @sel_reports = split(/,/,$new_reports{$_});
                map{
                    my $element_to_remove = $_;
                    @sel_reports = grep { $_ ne $element_to_remove } @
+sel_reports;
                 }@element_to_delete;
                if(scalar(@sel_reports) > 0) {
                    $new_reports{$_} = join(",",@sel_reports);
                } else {
                    delete $new_reports{$_};
                }
            }
}


print Dumper(\%new_reports);
[download]