There is a special variable $. that always contains the current line number of the file you are reading, starting with one. This can be used as the index for your two parallel arrays:

use strict;
use warnings;
use Data::Dumper;
my @array;
my @arraynew;
while(<DATA>){
  chomp;
  ( $array[$.-1], $arraynew[$.-1] ) = split ' ', $_, 2;
}
print Dumper \@array, \@arraynew;
__DATA__
1 http:/abcd efgh/
2 http:/
[download]

Update 1: corrected split statement as per comments below.

Update 2: another version based on regexes instead of using split:

use strict;
use warnings;
use Data::Dumper;
my @array;
my @arraynew;
( $array[$.-1], $arraynew[$.-1] ) = /^(\S+)\s(.*)/ while <DATA>;
print Dumper \@array, \@arraynew;
__DATA__
1 http:/abcd efgh/
2 http:/
[download]