But to go beyond perturbation, determinants lead to salvation

SAS's limerick:

There once was a lad from the Adriatic
who grew up among things Croatic
but he then crossed the pond
and became quite well known
for perturbing potentials quadratic.

But to go beyond perturbation
determinants lead to salvation:
just expand in a set
whose completeness is met
and get the result through summation.

This approach will lead us through the maze
well applied, it will solve every case -
from chaotic the flow
to the mystery of thought -
all is done by computing the trace.