comm -13 file1 file2 > file3

##</code><code>##

open FIRST,"file1" or die "$!: file1\n";
open LAST,"file2" or die "$!: file2\n";
open NEW,">file3" or die "$!: file3\n";
my %names = ();
my %n2 = ();
while (<FIRST>) {
   /^(\S+)/;
   $names{$1} = 1;
}
close FIRST;
while (<LAST>) {
   /^(\S+)/;
   $names{$1} or $n2{$1} = $_;
}
close LAST;
print NEW $n2{ $col1 } for my $col1 ( sort keys %n2 );
close NEW;