PLOTTEXT:subscript_mode

example

          <H0.5><S1>Sub-scripts are easy X<_>ABC<^>
          Multiple levels of sub_scripts are allowed
          Just remember to go "up" as many
          times as you go "down"
          <S3><H2><UPSILON><_><THETA><_><PSI><_>5<^><^><^><->
          <H.5>and back to normal