use strict;
use warnings;

my %HoH = (
    SUB1 => {
        Test1 => {
            value1   => "2300",
            value2   => "0.01",
        },
        Test2 => {
            value1   => "5000",
            value2     => "0.34",
        },
    },
    SUB2 => {
        Test1 => {
            value1   => "2800",
            value2   => "0.05",
        },
    },
);

my %hoa;
for my $I (sort keys %HoH){
  for my $J (sort keys %{ $HoH{$I}  })  {
    for my $K (sort keys %{  $HoH{$I}{$J} } ){
     push @{$hoa{$J}}, [$I,$K, $HoH{$I}{$J}{$K}];
    } 
  }
}


for my $k (sort keys %hoa){
  my $entry=$hoa{$k};
  print "For $k\n";
  for my $item(sort {$a->[1] cmp $b->[1] } @$entry){
    print "   $item->[0] has $item->[1]=$item->[2]\n" 
  }
}
__OUTPUT__
For Test1
   SUB1 has value1=2300
   SUB2 has value1=2800
   SUB1 has value2=0.01
   SUB2 has value2=0.05
For Test2
   SUB1 has value1=5000
   SUB1 has value2=0.34
[download]

Thanks all! NetWallah, your example seems exactly what I'm looking for. Time to study it and learn some new things about sorting hashes :) Please tell me how to only display the biggest value. Output example:

__OUTPUT__
For Test1
   SUB2 has value1=2800
   SUB2 has value2=0.05
For Test2
   SUB1 has value1=5000
   SUB1 has value2=0.34
[download]

Ok - here you go (Improved names of variables), and did "max" as requested:

my %rehash;
for my $SUBNAME (sort keys %HoH){
  for my $testname (sort keys %{ $HoH{$SUBNAME}  })  {
    for my $value_name (sort keys %{  $HoH{$SUBNAME}{$testname} } ){
     my $val =  $HoH{$SUBNAME}{$testname}{$value_name};
     if (exists  $rehash{$testname}{$value_name}
         and      $rehash{$testname}{$value_name}[1] > $val){
       # Do not update - greater value exists
     }else{
       $rehash{$testname}{$value_name} = [$SUBNAME,  $val];
     }
    } 
  }
}


for my $testname (sort keys %rehash){
   print "For $testname:\n";
   for my $value_name(sort keys %{ $rehash{$testname} }){
     print "   $rehash{$testname}{$value_name}[0] has $value_name\=$re
+hash{$testname}{$value_name}[1]\n";
  }
}
[download]

             I hope life isn't a big joke, because I don't get it.
                   -SNL

my %HoH = (
    SUB1 => {
        Test1 => {
            value1   => "2300",
            value2   => "0.01",
        },
        Test2 => {
            value1   => "5000",
            value1     => "0.34",
        },
    },
    SUB2 => {
        Test1 => {
            value1   => "2800",
            value2   => "0.05",
        },
    },
);
for my $sub_key (sort {$HoH{$a}{Test1}{value1} <=> $HoH{$b}{Test1}{val
+ue1} }keys %HoH){
   print "$HoH{$sub_key}{Test1}{value1}\n";
}
[download]

Try this

## Fort test1

## sort in descending order by value1, select first
@values1 = map { $_, $HoH{$_}{'Test1'}{'value1'} }
    sort { $HoH{$b}{'Test1'}{'value1'} <=> $HoH{$a}{'Test1'}{'value1'}
+ } keys %HoH;

## sort in descending order by value2, select first
@values2 = map { $_, $HoH{$_}{'Test1'}{'value2'} }
    sort { $HoH{$b}{'Test1'}{'value2'} <=> $HoH{$a}{'Test1'}{'value2'}
+ } keys %HoH;

print "Fort Test1\n";
print "  ", $values1[0], " has value1=", $values1[1], "\n";
print "  ", $values2[0], " has value2=", $values2[1], "\n";

## For test2

## sort in descending order by value1, select first
@values1 = map { $_, $HoH{$_}{'Test2'}{'value1'} }
    sort { $HoH{$b}{'Test2'}{'value1'} <=> $HoH{$a}{'Test2'}{'value1'}
+ } keys %HoH;

## sort in descending order by value2, select first
@values2 = map { $_, $HoH{$_}{'Test2'}{'value2'} }
    sort { $HoH{$b}{'Test2'}{'value2'} <=> $HoH{$a}{'Test2'}{'value2'}
+ } keys %HoH;

print "Fort Test2\n";
print "  ", $values1[0], " has value1=", $values1[1], "\n";
print "  ", $values2[0], " has value2=", $values2[1], "\n";
[download]

Enjoy!