$mech->click_button(name => 'ctl00$Main$Send_Button');

Is the name of the submit button literally 'ctl00$Main$Send_Button' ? Or are $Main and $Send_Button variables? Variables do not interpolate inside single quotes.

ive read about the postback and what i know so far is that i have to get the value of the __viewstate, __eventvalidation, select the Main send button value and submit the form however i dont know how to get the value of __eventstate which would be something like this

Again, Mechanize shouldn't change the values of form fields that are there already. If you need to extract the values of existing form fields, use my $viewstate = $mech->value( '__VIEWSTATE' );