"CASE" is not a variable

Hi All,

The following is a section of code inside an SQL function.   When I attempt to
run it I get the error message '"CASE" is not a variable'.  If I split this into
two queries (one for each variable) it works fine.  Obviously I have a work
around but I would like to understand what I am doing wrong.  TIA

SELECT tbl_item_bom.so_subline INTO v_so_subline,      CASE WHEN tbl_mesh.mesh_type = 'square' THEN                (
CASEWHEN tbl_mesh.unit_of_measure = 'in' THEN          
 
tbl_mesh.mesh_size                       WHEN tbl_mesh.unit_of_measure = 'ft' THEN 12.0    *
tbl_mesh.mesh_size                       WHEN tbl_mesh.unit_of_measure = 'mm' THEN 25.4    *
tbl_mesh.mesh_size                       WHEN tbl_mesh.unit_of_measure = 'cm' THEN  2.54   *
tbl_mesh.mesh_size                       WHEN tbl_mesh.unit_of_measure = 'm'  THEN  0.0254 *
tbl_mesh.mesh_size                       ELSE 0                  END                )      WHEN tbl_mesh.mesh_type =
'diamond'THEN                ( CASE WHEN tbl_mesh.unit_of_measure = 'in' THEN          
 
tbl_mesh.mesh_size / 2.0                       WHEN tbl_mesh.unit_of_measure = 'ft' THEN 12.0    *
tbl_mesh.mesh_size / 2.0                       WHEN tbl_mesh.unit_of_measure = 'mm' THEN 25.4    *
tbl_mesh.mesh_size / 2.0                       WHEN tbl_mesh.unit_of_measure = 'cm' THEN  2.54   *
tbl_mesh.mesh_size / 2.0                       WHEN tbl_mesh.unit_of_measure = 'm'  THEN  0.0254 *
tbl_mesh.mesh_size / 2.0                       ELSE 0                  END                )      ELSE 0      END INTO
v_mesh_sizeFROM sales_order.tbl_item_bom LEFT JOIN peachtree.tbl_mesh   ON tbl_item_bom.item_id = tbl_mesh.item_idWHERE
tbl_item_bom.so_number= rcrd_line.so_number  AND tbl_item_bom.so_line = rcrd_line.so_line  AND
tbl_item_bom.component_type= 'net';
 

Kind Regards,
Keith