ruby, using regex to find something in between two strings

Question

Using Ruby + regex, given:

starting-middle+31313131313@mysite.com

I want to obtain just: 31313131313

ie, what is between

Answer 1

Between 1st + and 1st @:

to[/\+(.*?)@/,1]

Between 1st + and last @:

to[/\+(.*)@/,1]

Between last + and last @:

to[/.*\+(.*)@/,1]

Between last + and 1st @:

to[/.*\+(.*?)@/,1]