When you have CSV data, it's best to use a CSV parser:

https://metacpan.org/pod/Text::CSV

There is a good amount of sample code for you right there in the docs. However, your particular error is one of scoping and array index syntax.

#!/usr/bin/env perl
use strict;
use warnings;
use v5.10;

use Text::ParseWords;

my $file = $ARGV[0] or die "Need a CSV file";
open my $fh, '<:encoding(UTF-8)', $file or die "Oops: $file $!";

while (my $line = <$fh>) {
    chomp $line;
    my @fields = quotewords(',',0,$line);
    for my $i (0..$#fields) {
        say "$i $fields[$i]";
    }
}
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Please note that the entire code block above is untested and I've never used Text::ParseWords. I simply built an example from your supplied attempt.