$ perl -MBenchmark=cmpthese -wE'my$x=join" "=>"",("aaa")x5,"";say"sourc: |$x|";sub splt{split" ",$x,1};sub rgx{$x=~s/^\s+//r};say "split: |",splt(),"|";say"regex: |",rgx(),"|";cmpthese(-2,{splt=>\&splt,rgx=>\&rgx})' sourc: | aaa aaa aaa aaa aaa | split: |aaa aaa aaa aaa aaa | regex: |aaa aaa aaa aaa aaa | Rate rgx splt rgx 3382502/s -- -58% splt 7989872/s 136% --