$mech->find_all_links(text_regex => qr/download/i);

##</code><code>##

/\d/         # contains a digit
/^\D*$/      # doesn't contain a digit

/[abc]/      # contains either the letter a, b, or c
/^[^abc]*$/  # doesn't contain a, b, or c

/foo|bar/    # contains foo or bar
???          # doesn't contain foo or bar