As many fellow monks have said, it is really a matter of taste. Ruby is hot right now, no doubt, perhaps hotter than Perl. However, Perl is much more mature and has CPAN. So I guess both are great for building the so called industrial-strength applications.
Technically Ruby is yet-another-language that copied Perl and added a complete object system (which came late in Perl). Its syntax is pretty much a ripoff from Perl. This is why Larry Wall
considers it the biggest 'threat' to Perl's 'ecological niche'.
So I guess this is why it is a matter of taste. There is no much distinction in technology (they are both dynamic, general-purpose languages), no difference in speed( Perl is a little faster), and also both are supported by vibrant communities.
I will stick with Perl because I know it is THE one of its kind. It took others a decade to fully realize the real power of the language and now that we have all these clones around, perhaps Perl 6 will be the next big thing.