use strict;
use warnings;

my $inFileStr = <<STR;
IM,BEN01,D,0
IM,BEN02,D,0
IM,BEN03, ,0
IM,BEN04, ,0
IM,BEN05, ,0
IM,BEN06,C,0
IM,BEN07, ,0
IM,BEN08, ,0
IM,BEN09, ,0
IM,BEN10,D,0
STR
my $first;

open my $inFile, '<', \$inFileStr or die "Can't open input file: $!\n";

while (<$inFile>) {
    chomp;

    my @data = split /,/;

    if ($data[2] =~ /^(D|C)$/) {
        print " > $first.txt\n" if defined $first;
        print "type $data[2] ";
        $first = $data[1];
    }

    print "$data[1].txt ";
}
close $inFile;

print " > $first.txt\n" if defined $first;

##</code><code>##

type D BEN01.txt  > BEN01.txt
type D BEN02.txt BEN03.txt BEN04.txt BEN05.txt  > BEN02.txt
type C BEN06.txt BEN07.txt BEN08.txt BEN09.txt  > BEN06.txt
type D BEN10.txt  > BEN10.txt