Example, this searches the current directory including subdirectories and presents a prompt for deletion:

fdupes ./ -r -d

In the prompt presented use the following to select rows matching the string:

sel

The selection can be inverted with

isel

Mark selected rows for keeping with

ks

Each entry has to be accepted by pressing enter. When rows has been accepted, delete the ones not selected with

prune

When done, exit the prompt with

quit