Learning regular expressions
Giovanni Organtini · IRIS Research product catalog (Sapienza University of Rome) · 2003
The simplest regular expression is a plain alphanumeric string. Such a regexp matches with all strings containing its content as a substring. As an example, consider the following verse from Cenerentola, my favorite opera by G. Rossini: ``Zitto, zitto, piano, piano, senza strepito e rumore.'' The regexp /piano/ is said to match with the verse, because the latter contains the same characters, with the same sequence, of the regexp.