This is a cool ruby feature to find substring.

# [] - works like `match` method, but return substring, not #<MatchData "...">
'string'[/str/] #=> "str"
# The real benefit you get when you find part of substring
'string'[/s(t)r/, 1] #=> "t"
'string'.match(/s(r)r/)[1]
#=>
# NoMethodError: undefined method `[]' for nil:NilClass
#   from (irb):3

# And the coolest thing that it can be used without tmp variables
'string'[/s(r)r/, 1] #=> nil

And real live code example

#get country code from the phone
'+12345678901'[/+(.*)\d{10}/, 1]

Of course there are not all abilities of String#[] method. And you should be confident with using nil as returned value. So check out the Ruby docs for more info. Or RubyTaps #99.