$ perl testMonth.pl 
Benchmark: running inlineArrayLookup, preBuiltArrayLookup, strftimeLookup, strftimeSubLookup, substrLookup, each for at least 2 CPU seconds...
inlineArrayLookup:  2 wallclock secs ( 2.12 usr +  0.00 sys =  2.12 CPU) @ 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 CPU) @ 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 substrLookup 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%                  --