str = "Ruby programming language is amazing!"
//.class # => Regexp
str =~ /R/ #return the index of the first occurrence => 0
str =~ /m/ # => 11
/ing/ =~ str # you can also flip it around => 13
"sky" =~ /[aeiou]/ # you can use a list of characters to match => nil
"love" =~ /[aeiou]/ # => 1
"%^%$%$" =~ /[a..z]/ # => nil