Another possible solution can be: 
while (<DATA>) {
  print "match on $1 and no 2nd$2\n" if /\S+ (\d+) \S+ (?:\d+)/;
}

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In reply to Re: regex search valid only if registers n and n+1 are equal? by sh1tn
in thread regex search valid only if registers n and n+1 are equal? by Voronich

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