$regex = RegexBuilder::create()
    ->start()
    ->letter()->repeated()->captureAs('office')
    ->string('_')
    ->number()->repeated(3)->captureAs('id')
    ->end()
    ->getRegex();
    
preg_match($regex, 'OfficeName_123', $match); // Returns TRUE

$regex = RegexBuilder::create()
    ->start()
    ->letter()->repeated()->captureAs('firstWord')
    ->string('_')
    ->matchCaptured('firstWord')
    ->string('_')
    ->number()->repeated()
    ->end()
    ->getRegex();
    
preg_match($regex, 'bar_bar_0293', $match); // Returns TRUE