Replace a string matched by certain regexp with its length in Vim

Question

In Vim, how do I replace a string matched by certain regexp with its length, like this:

Regexp = "\w*"

"hello" -> "5"
"bye" -> "3"

Is it possible to do it with :s or do I need to write some script?

Best regards

Answer 1

Replace 'hello' with your regex expression and this should work in VIM:

:s/hello/\=strlen(submatch(0))/