Register account using cURL

Shell Programming and Scripting
1

Hello!
I am trying to register account in Dropbox using cURL. There are a lot of existing examples doing POST and other useful stuff, however it doesn't work for me. Using formpost.pl script i got info:

--- FORM report. Uses POST to URL "/register"
Input: NAME="t" VALUE="vYTBqgxqCrt8K_prIXSHBkxt" (HIDDEN)
Input: NAME="fname" (TEXT)
Input: NAME="lname" (TEXT)
Input: NAME="email" (EMAIL)
Input: NAME="password" (PASSWORD)
Input: NAME="tos_agree" (CHECKBOX)
Input: NAME="register-submit" VALUE="1" (HIDDEN)
Input: NAME="register-submit-dummy" VALUE="Create account" (SUBMIT)
--- end of FORM

but when i mix it together

curl -d "t=XraVy8NxB2XE2nRnILrAWUUF&fname=first_name&lname=last_name&email=myacc@mymail.com&password=myacc@mymail.com&tos_agree=1&register-submit=1&register-submit-dummy=Create account" --location --output tmp/post.html "http://dropbox.com/register"

as result i get the same register page =\

i noticed that form has property onsubmit="return Forms.submitOnlyOnce();" and i don't know what variable i should set for checkbox. And as i understand "t" value is generated each time i open this page.

Maybe, someone have solved such a kind of problems or have interesting ideas... Anyway, thank you for response!