Replace in notepad++ using regex

Question

I have many line with the structure:

start...ABC...

In notepad++, how to replace ABC in all the lines start by start by another string (for example DEF)

Answer 1

The regex would be:

Find what: ^(start.*)ABC

Replace with: $1DEF

^ - tells that regex should start at the start of the line and $1 will match whatever matched in first group, which is (start.*)