Handles single letter usernames, initial / trailing / consecutive periods, max length of 30 letters.

check if the phone number is correct, updated to 2018. controlla che il cellulare sia corretto, aggiornata al 2018

Parse the Accept request HTTP header advertises which content types, expressed as MIME types, https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept

X3D bboxSize Three-tuple floating-point values with optional scientific notation, bounded non-negative or else -1 -1 -1 sentinel value. Derived from SFVec3f http://www.web3d.org/specifications/X3dRegularExpressions.html#bboxSize

further editing is required in code to get the filename without extension

The username should be at least 2 characters long, can have lower and uppercase letters, and can only have numbers in the end.

Primer ejercicio del Curso de Expresiones Regulares

Curso de Expresiones Regulares: Modos

Curso de Expresiones Regulares: Meta Caracteres

Curso de Expresiones Regulares: Cuantificadores y Repetición