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