Programming :: Irregular 2D Array In Shell Script

I am trying to create a shell script to automate a process that takes inputs from two sets of data. The variable SHELL in my system echoes as /bin/tcsh, but I see that my /bin directory has other possibilities, such as bash. So, if changing the shell could simplify my problem, then I would go with that.

I have a list of files containing data about objects, say
obj1.dat, obj2.dat, .... objn.dat, where n is around 20 (it varies).
These objects belong to a few different categories, and there are files detailing the properties of the categories, say
cat1.prop, cat2.prop, ... catm.prop, where m is smaller than n (more than one object in each category).

I know that shell scripts can handle 2-d arrays, although I am not sure how. The thing here is that category 1 could have 5 objects and category 3 could have 7 objects. So, this could produce a 2-d array, but not a rectangular one. I need to process these files taking into acount the data about the object and the properties of the category the object belongs to. Here is what I tried to do:

# First I enter a list of category names and m lists of objects in each category
category='cat1 cat2 cat3 ... catm'
cat1-obj='obj1 obj2 obj3'
cat2-obj='obj4 obj5'
cat3-obj='obj6 obj7 obj8 obj9 obj10'
.
.
.
catm-obj='objx objy objz objn'

# The lines above show the irregular 2-d array. Then I try to trick the script into parsing through this irregular 2-d array:
for i in $category
do
data='$i -obj'
for j in $data
do
mycommand $j.dat $i.prop > $j-$i.out
done
done

The line "mycommand $j.dat ..." is just the line that processes the information. That has been tested to work fine. Feeding the information to this is what does not work. The lines " data='$i-obj' " and " for j in $data " do not have the desired effect. I have tried other ways, like data=`echo $i "-obj"` and things of the sort, by to no avail.