Newer Perls (>=5.10) also allow you to say 

s/(.)\1\1\K\1*//g;

[download]

i.e., through the use of \K, you don't need to copy the part of the match you want to keep ($1 in your regex) into the substitution.

In reply to Re^2: Supress similar chars in the string by Anonyrnous Monk
in thread Supress similar chars in the string by Lana

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