Show us a few lines of your input which trigger the warning message, preferably as a self-contained code sample using __DATA__: 
while(<DATA>) {
    s/(\d),(?=\d)/$1|$2/g;
    print;
}
__DATA__

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In reply to Re: regex match triggers "Use of unititialized value ..." warning by toolic
in thread regex match triggers "Use of unititialized value ..." warning by mikeraz

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