my $column_separator = ",";

##</code><code>##

my $column_separator = qr/,/;

##</code><code>##

my $column_number = "3";

##</code><code>##

open(FILE,"<","$file");
while (<FILE>) {
 my @columns = split(/$column_separator/);
 print $columns[$column_number],"\n";
}
close FILE;