What are Ruby's numbered global variables

Question

What do the values $1, $2, $\', $` mean in Ruby?

Answer 1

The non-numbered ones are listed here:

https://www.zenspider.com/ruby/quickref.html#pre-defined-variables

$1, $2 ... $N refer to matches in a regex capturing group.

So:

"ab:cd" =~ /([a-z]+):([a-z]+)/

Would yield

$1 = "ab"
$2 = "cd"