Trying to capitalise first letter of sentences

[barha123]

Hello! I am trying to capitalise the first letters of sentences using the following expression:

"(?<=^|[.!?]\s|\n)([a-zA-Z])(?!.)"
->
"\U$1"

Doesnt seem to work, it return \U before the expression it caught (the equivalent to $1)
For instance:

aaaa. bbbb, cccc
will return \Uaaaa. \Ubbbb, cccc

Thanks for helping

[No3371]

I'm not very sure about how Electron app works but It seems like the \U and \L support is not included in Obsidian runtime.
It does not work in RegExr too, but works in VSCode.
I guess it's not very universally supported.