my $re = qr/
             <p>         # paragraph-open
             (           # Capture
              (?:         # group
               (?!<\/p>)    # Make sure we aren't at a paragraph-close
               (?!\[tab\])  # and we're not at [tab]
               .            # consume a char
              )*          # any number of times
              \[tab\]     # consume [tab] (hooray!)
              .*?        # anything up to paragraph-close
             )
             <\/p>               /x;