I think it is all in perldoc File::Find. Even if you do not want a solution, here is one ;-)

use File::Find;
use HTML::LinkExtor;
my @files;
find(
  {
    wanted => sub { -f && /\.ht/ && push @files, $File::Find::name }
  },
  @ARGV
);

my $p = HTML::LinkExtor->new(
  sub {
    my ( $tag, %attr ) = @_;
    return if $tag ne 'a';
    print $attr{href}, "\n";
  }
);

$p->parse_file($_) for (@files);
[download]

Call it this way: perl script.pl dir ...