regex - Emacs regexp replace situation -

on emacs

let have text:

abcd abcd. 23 . 2 important catching

with \. [[:digit:]] can catch pattern how replace without .

output should abcd abcd 23.

you use capturing groups retain numeral.

replace regexp:  \. ([[:digit:]]) replace regexp with:  \1 

the \1 refers numeral captured using ([[:digit:]]).