use strict; use warnings;

sub foo(){ 'x' }

$_ = -foo; # Ambiguous use of -foo 
           # resolved as -&foo() at ./ol line 8.

print; # '-x'

sub bar() { -1 }
$_ = -bar; #Ambigous ... as -&bar() ...
print; # 1 !not "--1"

my %h = ( -foo => 'FOO' );
print keys %h,' : ',$h{-foo}; # '-foo : FOO'