I'm sorry that didn't work. I don't do much with perl, but I do know that when you invoke your script with:

Code:

perl extract.pl FILE 3 0, 1, 3..6, 21..33

all that your script is seeing when setting $cols with:

Code:

my $cols = shift;

is 0,. Getting rid of the spaces in the argument list or quoting the args as in:

Code:

perl extract.pl FILE 3 "0, 1, 3..6, 21..33"

would get rid of that problem, but neither of them will convert the string into a list of numbers.