$ PERL5OPT= perl pm_11113750_x.pl
Name "main::count4" used only once: possible typo at pm_11113750_x.pl line 147.
=== Test 1: roughly equivalent speed
Benchmark: timing 5 iterations of uv_fits_double3, uv_fits_double_bitfiddle...
uv_fits_double3: 28 wallclock secs (27.22 usr +  0.08 sys = 27.30 CPU) @  0.18/s (n=5)
uv_fits_double_bitfiddle: 27 wallclock secs (26.72 usr +  0.00 sys = 26.72 CPU) @  0.19/s (n=5)
33046878 33046878 (48000004)

=== TEST 2: twiddle has an advantage if we don't use SvUV()
Benchmark: timing 10000 iterations of bitfiddle_3x, double3x, empty_func, empty_loop...
bitfiddle_3x: 18 wallclock secs (18.39 usr +  0.00 sys = 18.39 CPU) @ 543.74/s (n=10000)
  double3x: 30 wallclock secs (29.55 usr +  0.00 sys = 29.55 CPU) @ 338.44/s (n=10000)
empty_func:  0 wallclock secs ( 0.00 usr +  0.00 sys =  0.00 CPU)
            (warning: too few iterations for a reliable count)
empty_loop:  0 wallclock secs ( 0.00 usr +  0.00 sys =  0.00 CPU)
            (warning: too few iterations for a reliable count)
33046875 33046875 48000000 1416858175