I did consider that, but since the strftime variant was already losing badly, it didn't seem critical.

You're right, though, wrapping the fetch of @fixedLocaltime in a sub (returning a ref to the array) call kills the performance of the strftime variant a bit more.

$ perl testMonth.pl 
Benchmark: running inlineArrayLookup, preBuiltArrayLookup, strftimeLoo
+kup, strftimeSubLookup, substrLookup, each for at least 2 CPU seconds
+...
inlineArrayLookup:  2 wallclock secs ( 2.12 usr +  0.00 sys =  2.12 CP
+U) @ 513847.17/s (n=1089356)
preBuiltArrayLookup:  2 wallclock secs ( 2.09 usr +  0.01 sys =  2.10 
+CPU) @ 568700.00/s (n=1194270)
strftimeLookup:  1 wallclock secs ( 1.81 usr +  0.35 sys =  2.16 CPU) 
+@ 223003.24/s (n=481687)
strftimeSubLookup:  2 wallclock secs ( 1.74 usr +  0.26 sys =  2.00 CP
+U) @ 182455.50/s (n=364911)
substrLookup:  2 wallclock secs ( 2.19 usr +  0.01 sys =  2.20 CPU) @ 
+446835.91/s (n=983039)
                        Rate strftimeSubLookup strftimeLookup substrLo
+okup inlineArrayLookup preBuiltArrayLookup
strftimeSubLookup   182455/s                --           -18%         
+-59%              -64%                -68%
strftimeLookup      223003/s               22%             --         
+-50%              -57%                -61%
substrLookup        446836/s              145%           100%         
+  --              -13%                -21%
inlineArrayLookup   513847/s              182%           130%         
+ 15%                --                -10%
preBuiltArrayLookup 568700/s              212%           155%         
+ 27%               11%                  --
[download]

--
Mike

Edit by tye, change PRE to CODE around long lines