There is a module on CPAN, named HTML::TableExtractor or similar that should be able to help with your task.

Warnings about using regular expressions for HTML parsing aside, here is one approach that extracts data according to your pattern into a hash (named %price at a guess):

my $html = <<EOT;
stuff
Lumber:</td><td align="right"><b>10
more stuff
Clay:</td><td align="right"><b>20
glug
Iron:</td><td align="right"><b>30
blub
Crop:</td><td align="right"><b>40
stuff again
EOT

my %price;
$price{ lc $1} = $2 while 
    $html =~ m#(\w+):</td><td align="right"><b>(\d+)#ig;
my ( $lumber, $clay, $iron, $crop) =
    @price{ qw( lumber clay iron crop)};
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Anno