Thermal expansion expression

I want to change the coefficient of thermal expansion， but I cannot understand the original expression， who can explain it for me？ Thank you！

(alpha(T[1/K])[1/K]+(Tempref-293[K])if(abs(T-Tempref)>1e-3,(alpha(T[1/K])[1/K]-alpha(Tempref[1/K])[1/K])/(T-Tempref),d(alpha(T[1/K])[1/K],T)))/(1+alpha(Tempref[1/K])[1/K](Tempref-293[K]))