Improved the regular expression to work with Cyrillic and any other l…

[Serge044]

These code examples did not work properly with Cyrillic, so I proposed a solution. If it is approved, it will be also necessary to further describe it in the comments to this code so that it is clear what it is and why it is being done.

Brief explanations:

\p{L}: matches any letter (regardless of language).

u: indicates the use of Unicode.