line1 from PERSON 
changetype: modify 
replace: manager 
line1 from MGR 

line2 from PERSON 
changetype: modify 
replace: manager 
line2 from MGR 

...etc... 

#! perl -slw 
use strict; 
use warnings; 
use diagnostics; 
use constant batchdir => "c:\temp10"; 

open (PERSON,"f1"); 
open (MGR,"f2"); 
open OUT, ">", "buildAD.ldif" or die "Cannot write to 'buildAD.ldif': $!"; 
truncate (OUT, 0); 

my $line; 
my $line2; 

while ($line = <PERSON>) { 
#chomp; 
my @dn1 = split(/\s+/,$line); 
my $count = scalar(@dn1); 
print OUT "$line"; 
print OUT "changetype: modify"; 
print OUT "replace: manager"; 

while ($line2 = <MGR>) { 
#chomp; 
my @dn2 = split(/\s+/,$line2); 
my $count2 = scalar(@dn2); 
print OUT $line2, "\n", if ($count == $count2); 
} 
} 

close PERSON; 
close MGR; 
close OUT; 
exit;