Be sure to do as is described in the POD for LWP::Simple: Check your return values for success.

my $page = get("http://www.whoever.de");
die "Couldn't get the page!\n" unless defined $page;
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It could be that you're not even succeeding in fetching the page. Next, dump $page into a text file where you can examine it later to see if it really contains the text you're looking for (without any line-breaks, etc). If your HTML parsing needs get fairly elaborate, you might want to look at HTML::TokeParser anyway; use a powertool when a powertool is needed.