Altough the ampersand is not mandatory, I use it, in order to read my code easier. In my opinion it belongs to the structured perl programming style.

I would disagree. I think it is clumsy, confusing, needless and potentially problematic:

From perlfaq7:

What's the difference between calling a function as &foo and foo()?

When you call a function as `&foo', you allow that
function access to your current @_ values, and you by-pass
prototypes.  That means that the function doesn't get an
empty @_, it gets yours!  While not strictly speaking a
bug (it's documented that way in the perlsub manpage), it
would be hard to consider this a feature in most cases.

When you call your function as `&foo()', then you do get a
new @_, but prototyping is still circumvented.

Normally, you want to call a function using `foo()'.  You
may only omit the parentheses if the function is already
known to the compiler because it already saw the
definition (`use' but not `require'), or via a forward
reference or `use subs' declaration.  Even in this case,
you get a clean @_ without any of the old values leaking
through where they don't belong.

Tony