ERROR: cannot subscript type text because it is not an array

I have table with field l type lseg

Column | Type | Modifiers
--------+---------+-----------
cnt | integer |
used | boolean |
l | lseg |
c | text |

select l from t where used = false group by l[0];
ERROR: cannot subscript type text because it is not an array

select l from gcode where used = false group by l[0][0],l[0][1];
ERROR: cannot subscript type text because it is not an array

Using PostgreSQL 8.3.11
How can I work around this

Richard