perl -i.bak -nle 's/search/replace/g unless $. & 2; print' file

Your one-liner is not going to do what you think. $. & 2 is going to evaluate to true whenever the third second bit from the right (2 is binary 100) is set. Given this input file (lines.txt)

line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
line 9

[download]

adapting your one-liner to just print the lines gives

$ perl -nle 'print unless $. & 2;' lines.txt
line 1
line 4
line 5
line 8
line 9

[download]

Did you actually test your adaptation of GrandFather's idea before posting? Changing between odd and even is as simple as if $. & 1 and unless $. & 1. Perhaps you could have a look at "Bitwise And" in perlop to further your understanding.

Cheers,

JohnGG

Update: Corrected typo.

Update 2: Corrected huge balls-up, thanks fenLisesi. Where did I get "2 is binary 100" from?

Update 3: And thanks clinton, saw your reply after /msg from fenLisesi

In reply to Re^3: Search and replace in all odd lines by johngg
in thread Search and replace in all odd lines by greatshots

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