Two cool regex features

Unicode Character Properties

\p{spec}


where spec - various specs definitions like:

• L - letter
• Ll - lowercase letter
• P - punctuation
• Cyrillic - Cyrillic letter
• InSpecials: U+FFF0..U+FFFF

... and much more.

Character Class Subtraction

Example:

[a-z-[aeiuo]]


A single letter is not a vowel.


Could be combined with Unicode character properties: 

non-English letters - [\p{L}-[\p{IsBasicLatin}]]


More examples here