To quote the good book (Camel, 2nd ed., p115) almost verbatim:

&foo(1,2,3);  # pass three arguments.
foo(1,2,3);   # the same.

foo();        # pass a null list.
&foo();       # the same.

&foo;         # foo() gets current args, like foo(@_) !!
foo;          # like foo() IFF sub foo pre-declared, else bareword "fo
+o".
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The ampersand also disables any prototype checking on arguments not provided.

Which means that under certain circumstances, using the ampersand can lead to unexpected results, so in my case, I tend to avoid it in all sub calls, so I don't have to remember the details.

But I never called it evil, I just wanted folks to be aware that putting an ampersand in front of a sub call has odd behavior when no explicit arguments are passed. when I first read the Camel book, this section made me cringe.