Is it possible to make a minimal perfect hash function in this situation?

Question

I want to create a Hash Map (or another structure, if you have any suggestions) to store key value pairs. The keys will all be inserted at once at the same time as the map is cr

Answer 1

if you know the set of all possible variable names, then it would be possible to use to perfect hash the names to numbers

but each of the hash tables would end up having the same length an example is if X and y are the names then the map would always be of length 2

if perfect(str) turns 'x' and 'y' into 0 and 1; then the function get would be

get(field, table) 
{
   return table[perfect(field)];
}