Get rid of initial, trailing spaces, and extra middle spaces (more than one space in the middle of a string)

Curso de Expresiones Regulares: Cuantificadores y Repetición

Curso de Expresiones Regulares: Meta Caracteres

Curso de Expresiones Regulares: Modos

Primer ejercicio del Curso de Expresiones Regulares

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

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

This regex efficiently captures any U.S. state abbreviation in only 117 characters, as opposed to 159 characters to list each state individually.

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

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

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