Perl has an exponentiation operator (**, just like Fortran's ;-)), so x**n is easy. I believe, however, that Perl uses the C math library's pow routine (and 0**0 is undefined, and should return NaN, regardless of Perl's behavior, but I digress). In any case, writing a sub to calculate small integer powers, with little concern for efficiency, is quite easy. The factorials require a routine. Don't make the mistake of writing a recursive routine to calculate factorials; they are easily, and much more efficiently, calculated by a for loop.
Neither piece is particularly difficult. Beware, though, that numerical programming can be quite tricky when values get large or small. There is a wealth of information to be had, for example at na net and the Dictionary of Algorithms and Data Structures.
Information about American English usage here and here.
Any Northeastern US area jobs? I'm currently unemployed.