#!...
package main;
use strict;
use warnings;
use WWW::Mechanize ();
use File::Slurp qw( read_file write_file );
use Mail::Sendmail qw( sendmail );

use constant BALANCE_LOGIN =>
    ...;
use constant USERID  => ...;
use constant USERPIN => ...;

use constant BALANCE_FILE => ...;
use constant BALANCE_URL  =>
    ...;

use constant PHONENUMBER => ...;
use constant NOTIFY_URL  =>
    ...;

my $old_balance     = eval { return read_file(BALANCE_FILE) };
my $current_balance = eval {
    my $agent = WWW::Mechanize->new( autocheck => 1 );
    $agent->env_proxy();

    $agent->get(BALANCE_LOGIN);
    my $form = $agent->current_form;
    $form->value( SignOnID => USERID );
    $form->value( Password => USERPIN );
    $agent->submit();

    $agent->get(BALANCE_URL);

    local ($_) = $agent->content =~ /\$([\d.,]+)/mx;
    tr/,//d;
    return $_;
};
exit unless length $current_balance;

write_file( BALANCE_FILE, $current_balance );

my $difference = $current_balance - $old_balance;
if ( 0 != $difference ) {
    my $message = "\$$current_balance "
        . (
        $difference > 0
        ? "+$difference"
        : $difference
        );
    print "$message\n";

    my $agent = WWW::Mechanize->new;
    $agent->get(NOTIFY_URL);
    $agent->form_name('composeForm');
    my $form = $agent->current_form;
    $form->value( phoneNumber => PHONENUMBER );
    $form->value( message     => $message );
    $agent->submit();
}
[download]