Ok, what you want is \1 working as a group of chars. Well, we can't, but you can use some complexer code: 
  $var = "abXaaabbbc" ;
  $var =~ s/(..)X(??{"[$1]+"})/${1}#/ ;
  print "$var\n" ;

[download]
Output: 
ab#c

[download]

Graciliano M. P.
"Creativity is the expression of the liberty".

In reply to Re^3: \1, \2, \3, ... inside of a character class by gmpassos
in thread \1, \2, \3, ... inside of a character class by ccn

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