Oh thank you. The difference moved to 110 versus 220: 
              Rate rosetta_old rosetta_new     eertree
rosetta_old 20.0/s          --        -98%        -98%
rosetta_new  864/s       4222%          --        -27%
eertree     1177/s       5784%         36%          --

              Rate rosetta_old rosetta_new     eertree
rosetta_old 2.63/s          --        -99%       -100%
rosetta_new  215/s       8058%          --        -67%
eertree      654/s      24749%        205%          --
1..2

[download]

I missed the - $n because I was trying to get all the palindromes from the Rosetta code instead of just the unique ones. It seemed the new code worked correctly, but the old one didn't, so I started experimenting with replicating its incorrect output...

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re^5: Possessive sub-pattern with non-greedy content + recursion: WHY does this work?? by choroba
in thread Possessive sub-pattern with non-greedy content + recursion: WHY does this work?? by Anonymous Monk

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