use HTML::Parser;

$p = new HTML::Parser(start_h => [\&start, "tagname"],
                      end_h => [\&end, "tagname"],
                      default_h => [\&default, "text"]);

$p->parse($some_html);
$p->parsefile(\*SOME_FH);

sub start {
    my ($tagname) = @_;

    $in_a = 1 if $tagname eq 'a';
}

sub end {
    my ($tagname) = @_;

    $in_a = 0 if $tagname eq 'a';
}

sub default {
    my ($text) = @_;

    # do something with text if $in_a
}