First off: 'code smells' are coding styles that are fragile or hard to maintain (probably because they are hard to read). use strict helps address some forms of code smell if used sensibly. One thing that can make a huge difference is to ensure variables are used in the smallest sensible scope - strict helps that by telling you where an undeclared variable is first used.

A very closely related technique is to initialise scalar variables (variables that start with $) where they are declared. Sometimes array and hash variables can be usefully initialised where they are declared too, but often they are used to accumulate entries in following code and don't need an explicit initialisation value at declaration (they are born empty).

The golden rule: Always use strictures (use strict; use warnings; - see The strictures, according to Seuss).

Strictures, especially strict, tell you about things that are easy to get wrong and hard to find, like changing the spelling of an identifier. Using lexical variables (variables declared with my) limits their scope to the enclosing block (within the enclosing { } pair) which helps in understanding how variables are used and avoids misusing variables.

Fixing a bad smell can often end up with a jolly good clean out of the whole fridge to everyone's benefit. Adopting the use of strictures is a good start to cleaning up smelly code.