puzzling perl DBI vs psql problem

I have a weird issue that I can't figure out.

If I run the exact same query through psql as through perl DBI, I get
different results. I get far fewer results with DBI than through the psql
command line.

Any ideas why that would be?

The query is:
SELECT st.description, st.scene_thing_instance_id,
st.scene_id, sc.description, st.scene_thing_id, s.description,
st.position_x, st.position_y, st.position_z,
CASE
when (st.description = 'absolute root'::text) then 1
when (st.description ilike 'root%') then 2
else 3
END as s1, s.shape_name_id, sn.shape_name
from scene_thing_instances st
left join scene_things s on st.scene_thing_id = s.scene_thing_id
left join scenes sc on st.scene_id = sc.scene_id
left outer join shape_names sn on s.shape_name_id = sn.shape_name_id

order by s1, st.description

I get 14 rows back via psql, but I only get 5 rows back via DBI. It's very
puzzling.

I copied and pasted the query from the program's log file, so I know I'm
doing the exact same query. If it matters, I'm only seeing the rows with
'root' in them via DBI, which the CASE statement refers to.

Thanks,
Susan