How can I decode HTML entities?

Take a look at HTML::Entities:

use HTML::Entities;

my $html = "Snoopy & Charlie Brown";

print decode_entities($html), "\n";

You can guess the output.

The above answers tell you how to decode the entities into Perl strings, but you also asked how to change those into ASCII.

Assuming that this is really what you want and you don't want all the unicode characters you can look at the Text::Unidecode module from CPAN to Zap all those odd characters back into a roughly similar collection of ASCII characters:

use Text::Unidecode qw(unidecode);
use HTML::Entities qw(decode_entities);

my $source = '北亰';  
print unidecode(decode_entities($source));

# That prints: Bei Jing