Perfect. That code does what we want. Here it is.

#! perl
use strict;
use warnings;
use diagnostics;

open PERSON, "<", "ou3" or die "Cannot read 'ou3': $!";
open MGR, "<", "ou8" or die "Cannot read 'ou8': $!";
open OUT, ">", "buildAD.ldif" or die "Cannot write to 'buildAD.ldif': 
+$!";

truncate (OUT, 0);

while (defined (my $input1 = <PERSON>)) {
        my $input2 = <MGR> or die "No file MGR for $input1";
        chomp $input1;
        chomp $input2;
        print OUT $input1, "\n";
        print OUT "changetype: modify", "\n";
        print OUT "replace: manager", "\n";
        print OUT $input2, "\n\n";
}

close PERSON;
close MGR;
close OUT;
exit;
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