use strict;
use warnings;

my %data = ( 1 => { a => 10,
                    b => 5,
                    c => 20 },
             2 => { a => 90,
                    b => 15,
                    c => 40 } );

my @top_3 = (
             sort { $a->[-1] <=> $b->[-1] }
             map { my $k = $_;
                   my $h  = $data{ $_ };
                   map [ $k, $_, $h->{$_} ], keys %$h
                 } keys %data
            )[ 0..2 ];

for ( @top_3 ) {
  printf "\$data{%d}{%s} = %d\n",
    $_->[0], $_->[1],
    $data{$_->[0]}{$_->[1]};
}
__END__
$data{1}{b} = 5
$data{1}{a} = 10
$data{2}{b} = 15