lanx@ubuntu14-large:~$ perl
warn $];
warn \&CORE::GLOBAL::sleep;
warn \&CORE::sleep;
&CORE::GLOBAL::sleep(3);
__END__
5.018002 at - line 1.
CODE(0x1804cb8) at - line 2.
CODE(0x1830398) at - line 3.
Undefined subroutine &CORE::GLOBAL::sleep called at - line 4.