better way delete comma separated hash values?

The answer is in the question. Don't use comma separated hash values.

#!/usr/bin/perl

use warnings;
use strict;

use Data::Dumper;


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

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


print Dumper(\%new_reports);

my %ele_to_delete = map {$_=>1} @ele_to_delete;
for my $key ( @key_to_search ) {
   my $list = $new_reports{$key};
   @$list = grep !$ele_to_delete{$_}, @$list;
   delete $new_reports{$key} if !@$list;
}

print Dumper(\%new_reports);
[download]

Or if you had a HoH,

#!/usr/bin/perl

use warnings;
use strict;

use Data::Dumper;


my %new_reports = (
   10 => { map {$_=>1} qw( Test1 Test2 Test3 Test4 Test5 Test6 ) },
   20 => { map {$_=>1} qw( Test4                               ) },
);

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


print Dumper(\%new_reports);

for my $key ( @key_to_search ) {
   delete @{ $new_reports{$key} }{ @ele_to_delete };
   delete $new_reports{$key} if !%{ $new_reports{$key} };
}

print Dumper(\%new_reports);
[download]

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