for my $v ( values %Your_Hash_name ){
  $total += $v;
}

##</code><code>##

>perl -wMstrict -le
"my %hash = (
   '1'    => { 'Val1' => '13.12' },
   '2'    => { 'Val1' =>  '6'    },
   '3'    => { 'Val1' =>  '2'    },
   '4'    => { 'Val1' => '15.52' },
   );
 ;;
 my $total = 0;
 for my $v (values %hash) { $total += $v; }
 print $total;
 ;;
 $total = 0;
 for my $v (values %hash) { $total += $v->{Val1} }
 print $total;
"
73273728
36.64

##</code><code>##

>perl -wMstrict -le
"use List::Util qw(sum);
 ;;
 my %hash = (
   '1'    => { 'Val1' => '13.12' },
   '2'    => { 'Val1' =>  '6'    },
   '3'    => { 'Val1' =>  '2'    },
   '4'    => { 'Val1' => '15.52' },
   );
 ;;
 my $total = sum map $_->{Val1}, values %hash;
 print $total;
"
36.64