use strict;
use Time::HiRes;

my $x=*Time::HiRes::gettimeofday{CODE};
*Time::HiRes::gettimeofday = sub(){42};
print "Modified: ", Time::HiRes::gettimeofday,"\n";
*Time::HiRes::gettimeofday = $x;
print "Restored: ", Time::HiRes::gettimeofday