You placed a "bioinformatics" tag on your question. Many bioinformatics companies consider Perl programming to be quite important.
I suggest that you perform a search on "bioinformatics Perl" and take a look at books and sites that are retrieved. Perhaps you could park yourself at a local bookstore and peruse some of those titles. Free Perl interpreters are available.
You do have a basic understanding of genetics, yes? Be very familiar with some of the terminology, so you won't have to stare off into space while you pick from genotype/phenotype or mRNA/RNA/DNA or recall what a codon is.
It wouldn't hurt to nose around PubMed and get a basic understanding of what genomes are out there and what statistical tests can be performed on them.
I like your statistics idea. Perhaps you could write a program that tells you whether to accept or reject a null hypothesis based on numbers you read in from a file. Or perhaps you could figure out how to use the statistics portion of Entrez Gene in PubMed.
Best wishes for the interview.