Something like this:
use warnings;
use strict;

chomp(my @data_array=<DATA>);

print join $/ => map{$_->[0]}
      sort{$a->[1] <=> $b->[1]}
      map{[$_,(split/\s+/,$_,2)[1]]} @data_array;

__DATA__
AA 34
AB 22
AC 12

[download]
..produces.. 
AC 12
AB 22
AA 34

[download]
Update: And if the above is using too much power :), you can simply use a hash like so: 
my %hash;

 while(<DATA>){
  next if /^\s*$/;
  my @data = split;
  $hash{$data[1]} = $data[0]
}

  print $hash{$_},' ',$_,$/ for sort{$a<=>$b} keys %hash;

__DATA__
AA 34

AB 22

AC 12

[download]
Update 2: On the Hash method:
Please note that the keys used in the hash must be UNIQUE for the hash method to work properly as intended.
ww thanks for catching that.
If you tell me, I'll forget.
If you show me, I'll remember.
if you involve me, I'll understand.
--- Author unknown to me

In reply to Re: sorting first column by 2teez
in thread sorting first column by vis1982

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