A \n regex backreference is not active in a character class;  [^\1] is equivalent to  [^1]   (Update: Nope. Not quite. See Update below.)

Try: 

c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = 'CCHHHCHHCHC';
 print qq{'$s'};
 ;;
 $s =~ s/(\w) (?!\1). \1/$1$1$1/xgi;
 print qq{'$s'};
"
'CCHHHCHHCHC'
'CCHHHHHHHHC'

[download]
(note the use of the  /x modifier — for clarity only).

Update: In fact,  \1 in a character class is an octal escape sequence: 

c:\@Work\Perl\monks\flappygoat>perl -wMstrict -le
"my $s = qq{\1\x01\o{001}\cA};
 print 'match' if $s =~ /[^\1]/;
 print 'count: ', $s =~ tr/\1//;
"
count: 4

[download]
(no match; nothing printed). Wonderful what you can find out if you actually test stuff.

Give a man a fish:  <%-{-{-{-<

In reply to Re: Why my Regex doesn't work by AnomalousMonk
in thread Why my Regex doesn't work by flappygoat

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