Here are some raw timings I get, using the extensive word list I have for crosswords:

% perl -nwle 'END{ warn +(times)[0],"\n" }
  print $_
' /usr/share/dict/hv.words | wc -l
0.04
285520
% perl -nwle 'END{ warn +(times)[0],"\n" }
  print $_ if /^(.)(?!\1)(.)(?!\1|\2)(.)(?!\1|\2|\3)(.)(?!\1|\2|\3|\4)
+(.)$/
' /usr/share/dict/hv.words | wc -l
0.13
8632
% perl -MList::MoreUtils=uniq -nwle 'END{ warn +(times)[0],"\n" }
  print $_ if /^(?:(.)(.)(.)(.)(.)(?(?{ 5 != uniq $1, $2, $3, $4, $5 }
+)(?!)))$/
' /usr/share/dict/hv.words | wc -l
0.39
8632
% perl -MList::MoreUtils=uniq -nwle 'END{ warn +(times)[0],"\n" }
  print $_ if /^(.)(.)(.)(.)(.)$/ && 5 == uniq $1, $2, $3, $4, $5
' /usr/share/dict/hv.words | wc -l
0.1
8632
%

[download]

Oh, the anchor needs to come before the code block!

% perl -MList::MoreUtils=uniq -nwle 'END{ warn +(times)[0],"\n" }
  print $_ if /^(?:(.)(.)(.)(.)(.)$(?(?{ 5 != uniq $1, $2, $3, $4, $5 
+})(?!)))/
' /usr/share/dict/hv.words | wc -l
0.12
8632
%

[download]

I guess I was wrong (but it's important to get that anchor in the right place).

In reply to Re^6: Nonrepeating characters in an RE by hv
in thread Nonrepeating characters in an RE by BernieC

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