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

my %names ;
my $write_new = 0 ;
while (<FIRST>)
{
   /(\w*) (\d*)/ ;
   $names{$1} = $2 ;
}
close FIRST;

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

if ($write_new)
{
    open NEW,">","file3" or die "Can't open file3: $!\n";
    foreach (sort keys %names)
    {
        print NEW "$_ $names{$_}\n" ;
    }
    close NEW;
}