$ perl -MBenchmark=cmpthese -wE'my$x=join"    "=>"",("abc")x5,"";say"sourc: |$x|";sub trim{join" ",split" ",$x};sub rgx{$x=~s/^\s+//r=~s/\s+$//r=~s/\s\s+/ /gr};say "split: |",trim(),"|";say"regex: |",rgx(),"|";cmpthese(-2,{splt=>\&trim,rgx=>\&rgx})'
sourc: |    abc    abc    abc    abc    abc    |
split: |abc abc abc abc abc|
regex: |abc abc abc abc abc|
          Rate  rgx splt
rgx   506423/s   -- -71%
splt 1767763/s 249%   --