If I correctly understand the problem, you can do this using either:

  $string =~ s/([^Y])X+/$1/g;

[download]
or
  $string =~ s/([^YX])X+/$1/g;

[download]
depending on whether "YXX" should yield "YX" or be left unchanged.

Hugo

In reply to Re: Variable-width negative lookbehind by hv
in thread Variable-width negative lookbehind by dragonchild

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