Can you tell me what I am doing wrong here?

• You should use strict and warnings because they will give you clues to your problems.
• $hash{url} = $url2; will keep overwriting the last value of the literal key 'url' inside your for loop.
• Read perldsc.

use warnings;
use strict;

my @files = qw(
http://use.perl.org/
http://search.cpan.org/
http://jobs.perl.org/
);

my %hash = (
   curArray  => [],
   prevArray => [],
);

foreach my $url2 ( @files ) {
    push @{ $hash{url} }, $url2;
}

use Data::Dumper;
print Dumper(\%hash);

__END__

$VAR1 = {
          'prevArray' => [],
          'curArray' => [],
          'url' => [
                     'http://use.perl.org/',
                     'http://search.cpan.org/',
                     'http://jobs.perl.org/'
                   ]
        };
[download]

what does the curly braces around the hash do? ie. "@{ $hash{url} }"

And how come url is not defined in the original hash structure?

There should only be on url per hash entry entry in array.

array {
$url = "http://perl.org"
curArray = []
prevArray = []
}
[download]