use LWP::Simple;

sub getfeedencoding {
#takes: feed url
#returns: feed encoding based on what it says about itself in the XML header
#sample string: encoding="UTF-8"
    my $feedurl = shift;
    my $pagecontent = get($feedurl);
    $pagecontent =~ m{encoding="(.*?)"};
    return $1 or undef;
}

Get the character encoding of a feed

Perl