# [///](http://esolangs.org/wiki////) and [Retina](https://github.com/mbuettner/retina), 95 + 3 = 98 bytes

    /
    //
    
    This program wasn't written in \/\/\/, it was built for Retina!
    /?./....(.*)(R.*)!
    $2$1///!

+3 bytes for the `-s` flag in Retina.

## Explanation for ///

The first instruction is

    /
    //

removes all newlines from the rest of the code, resulting in

    This program wasn't written in \/\/\/, it was built for Retina!/?./....(.*)(R.*)!$2$1///!

Everything up to the `!` is just a literal and printed to STDOUT. The next instruction is

    /?./....(.*)(R.*)!$2$1/

But the search string `?.` cannot be found, so nothing happens. Then the remaining code is `//!` which is an incomplete instruction so the program terminates, having printed the correct string.

## Explanation for Retina

    /
    //

This tells Retina to replace `/` with `//`. But the input is empty, so this doesn't match anything.

    <empty>
    This program wasn't written in \/\/\/, it was built for Retina!

This replaces the input with the string in the second line.

    /?./....(.*)(R.*)!
    $2$1///!

This matches the string `\/\/\/, it was built for Retina!` and replaces it with `Retina, it was built for ///!` to give the correct result.