Ok. So you have to split the hashes from file1 and file2.

The following code should do it :

open FIRST,"file1" or die "Can't open file1: $!\n";
open LAST,"file2" or die "Can't open file2: $!\n";

my (%names1,%names2) ;
my $write_new = 0 ;

while (<FIRST>)
{
   /(\w*) (\d*)/ ;
   $names1{$1} = $2 ;
}
close FIRST;

while (<LAST>)
{
   /(\w*) (\d*)/ ;
   if (!defined($names1{$1}))
   {
      $write_new++ ;
   }
   $names2{$1} = $2 ;
}
close LAST;

if ($write_new)
{
   open NEW,">","file3" or die "Can't open file3: $!\n";
   foreach (sort keys %names2)
   {
      if (defined($names1{$_}))
      {
         print NEW "$_ $names1{$_}\n" ;
      }
      else
      {
         print NEW "$_ $names2{$_}\n" ;
      }
   }
   close NEW ;
}
[download]

I really feel my codes are dirty and unperlish. Is it just an idea ? Can any wise monk enlighten me about style ? I would be glad receiving cruel remarks about the above code :)

Gu