use Data::Dumper;

%input=(r=>[1..10],s=>[1..10],t=>[5..10],u=>[11..20]);

grep{$hash{"$input{$_}[0]_$input{$_}[-1]"}++;$tmp{$_}=$input{$_} if $hash{"$input{$_}[0]_$input{$_}[-1]"}==1}keys %input;

print Dumper(\%tmp);


##</code><code>##

use Data::Dumper;

%input=(r=>[1..10],s=>[1..10],t=>[5..10],u=>[11..20]);


grep{$hash{$input{$_}[0]}->{$input{$_}[-1]}++;$hash_1{$input{$_}[0]}++;$hash_2{$input{$_}[-1]}++;$tmp{$_}=$input{$_} if ($hash{$input{$_}[0]}->{$input{$_}[-1]}==1 && $hash_1{$input{$_}[0]}==1 && $hash_2{$input{$_}[-1]}==1 )}keys %input;

print Dumper(\%tmp);


Output:
$VAR1 = {
          'u' => [
                   11,
                   12,
                   13,
                   14,
                   15,
                   16,
                   17,
                   18,
                   19,
                   20
                 ],
          'r' => [
                   1,
                   2,
                   3,
                   4,
                   5,
                   6,
                   7,
                   8,
                   9,
                   10
                 ]
        };