Thanks a lot, that's what I am looking for. However now I get an error:

<h1>Software error:</h1>
<pre>Can't call method &quot;click&quot; on an undefined value at C:/P
+erl/site/lib/WWW/Mechanize.pm line 982, &lt;STDIN&gt; line 1.
</pre>
<p>
For help, please send mail to this site's webmaster, giving this error
+ message 
and the time and date of the error.
</p>
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perl:
use WWW::Mechanize;
my $ua = WWW::Mechanize->new();
$ua->get($url); # url page with button
$ua->click_button( number => 1 ); # there is only one button
print $ua->title;