Remember that split takes a regex as it first argument. Use a lookahead assertion after the comma.

use strict;
use warnings;
use Data::Dumper;
my $input = q|http://abc.org,http://de,f.org,https://ghi.org,http://jk
+l.org|;
my @urls = (split /,(?=http)/, $input, 4)[0..2];
print Dumper \@urls;
[download]

Output:

$VAR1 = [
          'http://abc.org',
          'http://de,f.org',
          'https://ghi.org'
        ];
[download]