Hello,

I am trying to write a script to take input in the form of "ABBCDE", and output all words which match that pattern. For example, "LOOKED" matches (note the repeated 'O', corresponding to the repeated 'B', and that all the other characters are mapped uniquely). Presently, my script takes the input an generates a regex. This is what it comes up with: 

/^(\w)([^\1])(\2)([^\1\2\3])([^\1\2\3\4])([^\1\2\3\4\5])\s/

[download]

What I was trying to express with this is:

  1. . Any character...
  2. . ...followed by anything that isn't the first character...
  3. . ...followed by what was found in (2)
  4. . ...followed by anything that isn't the first, second, or third match...

And so forth. The problem is that this regex also matches words like "SEEMED". This is bad, since that third E doesn't correspond to the input pattern. I am unsure why my regex is failing. Can anyone shed some light?

- Anonymous Monk

In reply to Matching Character Patterns With Backreferences by Anonymous Monk

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