[SQL] using a self referencing table

[drfrog]

i have a table with this structure

name (varchar)|category id (int4)|parent category id (int4)|leaf node
(bool)

im trying to make a perl script that should tree the info

parent cat
        subcat
                subcat2
                subcat2
        subcat  
                subcat2
...


but im having troubles wrapping my head around this

im using the Pg modules to access postgres

if anyone has any suggestions please lemme know thanks!