Scalars aren't necessarily one thing or another. There's no place to declare a scalar variable to be of type "string", or of type "number", or type "filehandle", or anything else. Perl is a contextually polymorphic language whose scalars can be strings, numbers, or references (which includes objects). While strings and numbers are considered pretty much the same thing for nearly all purposes, references are strongly-typed uncastable pointers with builtin reference-counting and destructor invocation.

You could find further infos on this article by Tom Christiansen: Is it a number?