Replace every other character

Question

how could i skip or replace every other character (could be anything) with regex?

"abc123.-def45".gsub(/.(.)?/, '@')

to get

"a@c@2@.@d@f@5"

Answer 1

Capture the first character instead, and write it back:

"abc123.-def45".gsub(/(.)./, '\1@')

It's important that you don't make the second character optional. Otherwise, in an odd-length string, the last character would lead to a match, and a @ would be appended. Without the ?, the last character will simply fail and remain untouched.

Working demo.