roboticus@Boink:~/funkytest$ ls
genfiles.pl  groupfiles.pl
roboticus@Boink:~/funkytest$ time ./genfiles.pl 

real    0m4.937s
user    0m1.644s
sys     0m3.292s
roboticus@Boink:~/funkytest$ ls | wc -l
49993
roboticus@Boink:~/funkytest$ time ./groupfiles.pl 
6712: 6712_WRW, 6712_DIK, 6712_FRB
8563: 8563_FHL, 8563_AAE, 8563_TSL, 8563_LCU
5006: 5006_SLA, 5006_PZK, 5006_PUB, 5006_FCK
8434: 8434_HNX, 8434_HPB, 8434_YED, 8434_SCB, 8434_KBS, 8434_CEH, 8434_JCH, 8434_NVN, 8434_VPN, 8434_GFM, 8434_BNJ
3509: 3509_EAY, 3509_WNU, 3509_MUI, 3509_NPX, 3509_LHX
7652: 7652_IMC, 7652_GMN
4863: 4863_MTN, 4863_RGD, 4863_BFT, 4863_LSF, 4863_KNJ, 4863_JGE
Files: 49991, Groups: 9922

real    0m0.736s
user    0m0.664s
sys     0m0.080s
roboticus@Boink:~/funkytest$ time rm {0,1,2,3,4,5,6,7,8,9}*

real	0m6.451s
user	0m3.044s
sys	0m3.212s
roboticus@Boink:~/funkytest$