Floats in Perl can be represented in all the ways that C would allow you to
Here are some examples for you:

0.1 
-123.4
-10e4  # (-10) times 10 to the fourth power
-10E4  # the same thing
-1E5   # Another way to say the same thing
-1e-6  # -1 * 10 to the -6th power

String literals in Perl have some interesting characteristics you should learn about.