use strict;
use warnings;
use feature 'say';
use Time::Piece;
use Class::Unload;

eval { say gmtime->datetime; 1 } or say $@;

Class::Unload->unload('Time::Piece');

eval { say gmtime->datetime; 1 } or say $@;

require Time::Piece;

eval { say gmtime->datetime; 1 } or say $@;

__END__