First off, if you are using a hash reference, you need braces, not parentheses:

my $hash = {
    foo => 'bar',
};
[download]

There are several approaches you can use.

Use single quotes for a double quote:

my $hash = {
    '"' => 1,
};
[download]

Quote the double quote:

my $hash = {
    "\"" => 1,
};
[download]

Use chr:

my $hash = {
    chr(34) => 1,
};
[download]

Use alternative quotes:/p>

my $hash = {
    q(") => 1,
};
[download]