print $target = time + 10; 
print $s and sleep $s while ( $s = ($target - time )/2 ) > 0; 
print time;;
1203221999.59375
5
2.49999403953552
1.24999451637268
0.624994039535522
0.312494516372681
0.15625
0.0781184434890747
0.0390595197677612
0.0155709981918335
0.00779902935028076
1203221999.59376