You almost had it:

#!/usr/bin/perl -l

use strict;
use warnings;
use WWW::Mechanize;

my $url = 'https://www.google.de/';

my $agent = WWW::Mechanize->new;
my $response = $agent->get($url);

my $link = $agent->find_link( text => 'Bilder' );
print 
  "The Google Bilder search URL is: ", Dumper ( $link->url );
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