Postorder

Score: 54.09 (pass)

#!perl -l
$_=pop;($~=pop)=~s}.}s~($&)(\w*)~
$2
$1~}eg;print//

Score: 54.09 (pass)

#!perl -l
$_=pop;($~=pop)=~s}.}s~($&)(\w*)~
$2
$1~}eg|print??

Score: 55.08 (pass)

#!perl -l
$_=pop;$ARGV[0]=~s}\w}s~($&)(\w*)~|$2|$1~}eg;print//

Score: 55.11 (pass)

#!perl -l
$_=pop;$ARGV[0]=~s!\w!s/($&)(\w*)/~$2~$1/!eg;print//

Score: 57.08 (pass)

#!perl -l
$_=pop;$ARGV[0]=~s}.}s~($&)(\w*)~|$2|$1~}eg;print/\w/g

Score: 58.11 (pass)

#!perl -l
for(s//@ARGV/;s/(\w)(.+)\1(\w*)/$2~$3~$1/;){}print/\w/g

Score: 59.12 (pass)

#!perl -l
for($_="@ARGV";s/(\w)(.+)\1(\w*)/$2~$3~$1/;){}print/\w/g

Score: 60.12 (pass)

#!perl -l
$_="@ARGV";9until!s/(.)(.+)\1(\w*)\b/$2~$3~$1/;print/\w/g

Score: 61.13 (pass)

#!perl -l
$_="@ARGV";9while s/(\w)(.+)\1(\w*)\b/$2 $3 $1/;print/\w/g

Score: 63.16 (pass)

#!perl -l
$_="@ARGV";9while s/(\w)(.+)\1(\w*) */$2 $3 $1/;y/ //d;print

Score: 96.14 (pass)

#!perl -l
sub p{p($`,$3),p(@_[1,3]),$_[0]if!!(@_="@_"=~/(.)(.*) \1((??{".{$-[1]}"}))(.*)/)}print p@ARGV

Score: 102.14 (pass)

#!perl -l
sub p{p(@_[0,3]),p(@_[2,4]),$_[1]if!!(@_="@_"=~/(.*)(.)(.*) \2((??{".{$+[1]}"}))(.*)/)}print p@ARGV

Score: 109.14 (pass)

#!perl -l
sub p{p(@_[1,3]),p(@_[2,4]),$_[0]if!!(@_="@_"=~/(.)(.*)(.*) ((??{".{@{[$+[2]-1]}}"}))\1(.*)/)}print p@ARGV

Score: 113.15 (pass)

#!perl -l
sub p{!!(@_="@_"=~/^(.)(.*)(.*) ((??{".{@{[$+[2]-1]}}"}))\1(.*)$/)&&(p(@_[1,3]),p(@_[2,4]),$_[0])}print p@ARGV

Score: 120.14 (pass)

#!perl -l
sub p{@_="@_"=~/^(.)(.*)(.*) ((??{".{@{[$+[2]-1]}}"}))\1(.*)$/;$_[1]&&p(@_[1,3]),$_[2]&&p(@_[2,4]),$_[0]}print p@ARGV