# Setup the Master list
open(MASTERFILE, ">>$dir/MasterList.csv")
   or die "Can't open MasterList.csv: $!";

# Set up a loop to "Do Stuff" tm
my @src_files = <$src_dir/*.csv>;
foreach my $src_file (@src_files) {

    open (INFILE, "$src_file")
        or die "Can't open $src_file for input: $!\n";

    while (<INFILE>) {
        chomp;

    #
    # Do Stuff Here!
    #

    open (OUTFILE, ">>$dest_file")
        or die "Can't open $dest_file for output: $!\n";

    print OUTFILE "Your records go here\n";
    print MASTERFILE "Your records go here\n";

    close OUTFILE;

}

close MASTERFILE;