If the URL is always the same, try this:

my $url = 'http://www.alwaysthesame.com';
s/"\($url\)"/"$url"/g;  # match all occurences
[download]

If the URL could be anything, try this:

s|"\((http://[^)]+)\)"|"$1"|g;
[download]

If you post more details about your data and the problem you are trying to solve, I'm sure we can come up with a more helpful solution.