How to deal with nameless forms on websites? - perl

Question

I would like to write a script that lets me use this website
http://proteinmodel.org/AS2TS/LGA/lga.html
(I need to use it a few hundred times, and I don't feel like doing that manually)
I have searched the internet for ways how this could be done using Perl, and I came across WWW::Mechanize, which seemed to be just what I was looking for. But now I have discovered that the form on that website which I want to use has no name - its declaration line simply reads
<FORM METHOD="POST" ACTION="./lga-form.cgi" ENCTYPE=multipart/form-data>
At first I tried simply not setting my WWW::Mechanize object's form_name property, which gave me this error message when I provided a value for the form's email address field:
Argument "my_email#address.com" isn't numeric in numeric gt (>) at /usr/share/perl5/WWW/Mechanize.pm line 1618.
I then tried setting form_name to '' and later ' ', but it was to no avail, I simply got this message:
There is no form named " " at ./automate_LGA.pl line 40
What way is there to deal with forms that have no names? It would be most helpful if someone on here could answer this question - even if the answer points away from using WWW::Mechanize, as I just want to get the job done, (more or less) no matter how.
Thanks a lot in advance!

Answer 1

An easy and more robust way is to use the $mech->form_with_fields() method from WWW::Mechanize to select the form you want based on the fields it contains.
Easier still, use the submit_form method with the with_fields option.
For instance, to locate a form which has fields named 'username' and 'password', complete them and submit the form, it's as easy as:
$mech->submit_form(
with_fields => { username => $username, password => $password }
);
Doing it this way has the advantage that if they shuffle their HTML around, changing the order of the forms in the HTML, or adding a new form before the one you're interested in, your code will continue to work.

Answer 2

I don't know about WWW::Mechanize, but its Python equivalent, mechanize, gives you an array of forms that you can iterate even if you don't know their names.
Example (taken from its homepage):
import mechanize
br = mechanize.Browser()
br.open("http://www.example.com/")
for form in br.forms():
print form
EDIT: searching in the docs of WWW::Mechanize I found the $mech->forms() method, that could be what you need. But since I don't know perl or WWW::Mechanize, I'll leave there my python answer.

Answer 3

Okay, I have found the answer. I can address the nameless form by its number (there's just one form on the webpage, so I guessed it would be number 1, and it worked). Here's part of my code:
my $lga = WWW::Mechanize->new();
my $address = 'my_email#address.com';
my $options = '-3 -o0 -d:4.0';
my $pdb_2 = "${pdb_id}_1 ${pdb_id}_2";
$lga->get('http://proteinmodel.org/AS2TS/LGA/lga.html');
$lga->success or die "LGA GET fail\n";
$lga->form_number(1);
$lga->field('Address', $address);
$lga->field('Options', $options);
$lga->field('PDB_2', $pdb_2);
$lga->submit();
$lga->success or die "LGA POST fail\n";