while (defined my $input1=<PERSON>) {
        my $input2 = <MGR> or die "No corresponding MGR for $input1";
        chomp $input1; 
        # Are you sure you want to chomp ? If so, you probably need \n when printing
        chomp $input2;
        print OUT $input1;
        print OUT "changetype: modify";
        print OUT "replace: manager";
        print OUT $input2, "\n";
}