It's a good practice to use many use vars lines to group variables with common semantic meaning.

Now two interesting points from the documentation:

use vars predeclare global variable names (obsoleted by our())

and...

An `our' declares the listed variables to be valid globals within the enclosing block, file, or `eval'. That is, it has the same scoping rules as a "my" declaration, but does not create a local variable. If more than one value is listed, the list must be placed in parentheses. The `our' declaration has no semantic effect unless "use strict vars" is in effect, in which case it lets you use the declared global variable without qual­ ifying it with a package name. (But only within the lexical scope of the `our' declaration. In this it differs from "use vars", which is package scoped.)