When you are using string interpolation, (as you should pr [Martin Büttner's post](http://codegolf.stackexchange.com/a/37519/4372)), you don't need the curly brackets if your object has a sigil (`$`, `@`) in front of it. Useful for magical variables like `$_`, `$&`, `$1` etc:

    puts "this program has read #$. lines of input"

So also if you need to print a variable more than you use it otherwise, you may save some bytes.

    a=42; puts "here is a: #{a}"; puts "here is a again: #{a}"
    $b=43; puts "here is b: #$b"; puts "here is b again #$b"