$i+=1/(($_+=1e-7)**2+1)until$_>1;print$i/1e7*4 #23456789_123456789_123456789_123456789_123456 # 1 2 3 4 #### $i+=($_&1?4:-4)/($_*2-1)for 1..1e6;print$i #23456789_123456789_123456789_123456789_12 # 1 2 3 4