use strict;
use WWW::Mechanize;
use YAML qw(DumpFile LoadFile freeze thaw);

# init a mech instance
my $mech = WWW::Mechanize->new();

# on first instance...
if(! -f 'stored_mech.dat') {
    # get, freeze, and store
    $mech->get('http://localhost/mech-form.php');
    DumpFile('stored_mech.dat', [freeze($mech)]);
    exit;
}
# on subsequent instance...
else {
    # retrieve, thaw, and submit form
    my $stored = LoadFile('stored_mech.dat');
    $mech = thaw($stored->[0]);
    $mech->submit_form(form_number=>1);
}