It is not possible, you have to be explicit. If you look at the debian packaging library code, the regular expression for a dependency is quite simple: http://anonscm.debian.org/gitweb/?p=dpkg/dpkg.git;a=blob;f=scripts/Dpkg/Deps.pm;h=449bafb23e782088cdd42e036146230627d05470;hb=HEAD#l593
It only match against a package name containing: [a-zA-Z0-9][a-zA-Z0-9+.-]*