$ perl -le 'foo; sub foo { print "foo" }'
$ perl -le '&foo; sub foo { print "foo" }'
foo

##</code><code>##

$ perl -wle 'foo; sub foo{ print "foo"}'
Unquoted string "foo" may clash with future reserved word at -e line 1.
Useless use of a constant in void context at -e line 1.