Working from pattern 'a|ab|abc|abcde|ef|gh|ghij|qrst|nqmz|stuv', qr='(?-xism:a|ab|abc|abcde|ef|gh|ghij|qrst|nqmz|stuv)'
preComp finds 6
preCompQR finds 6
noPrecomp finds 6
Benchmark: running noPrecomp, preComp, preCompQR, each for at least 3 CPU seconds...
 noPrecomp:  4 wallclock secs ( 3.09 usr +  0.01 sys =  3.10 CPU) @ 33414.22/s (n=103417)
   preComp:  4 wallclock secs ( 3.24 usr +  0.01 sys =  3.25 CPU) @ 35360.06/s (n=115097)
 preCompQR:  2 wallclock secs ( 3.08 usr +  0.02 sys =  3.10 CPU) @ 35094.39/s (n=108933)
             Rate noPrecomp preCompQR   preComp
noPrecomp 33414/s        --       -5%       -6%
preCompQR 35094/s        5%        --       -1%
preComp   35360/s        6%        1%        --