use strict;
use IO::File;

# load main file
my %main_data;
my $f = new IO::File "mainfile.txt", "r" or die "Can't open main db: $!";
while(<$f>) {
  chomp;
  my @res = split /\t/;
  $main_data{$res[2]}{data} = \@res; # 3rd field is the ID number
}
undef $f;

# load sort reference file
my $f = new IO::File "sort.txt", "r" or die "Can't open sort.txt: $!";
while (<$f>) {
  chomp;
  my ($id, $total) = split /\t/;
  if (exists $main_data{$id}) {
    $main_data{$id}{total} = $total; # insert additional values
  }
}

# sort the main db in descending order
my @sorted_id = sort { $main_data{$b}{total} <=>
                       $main_data{$a}{total} } keys %main_data;

# print sorted main db
print "@{$main_data{$_}{data}}\n" foreach @sorted_id;

##</code><code>##

mainfile.txt
------------
A       B       12
C       D       11
E       F       10

sort.txt
--------
10      120.00
11      200.00

##</code><code>##

C D 11
E F 10
A B 12