{ 
    local *Time::HiRes::gettimeofday = sub { print 42; }; 
    print Time::HiRes::gettimeofday(); 
};;
Subroutine Time::HiRes::gettimeofday redefined at (eval 4) line 1, <STDIN> line 2.
42
1
print Time::HiRes::gettimeofday();;
1172754765 437500