Let's start with some basic regular expression matchers. We'll begin with storing a string sentence in a variable:
string = "The quick 12 brown foxes jumped over 10 lazy dogs"
First off, let's check whether the preceding string contains the letter o, and to do that, write the following code:
p string =~ /o/
In Ruby, anything contained within // is a regular expression.
Now if you execute this code, the output should be 15. The value printed out would be 15 because the matcher would find the letter o at position 15.
If you want to find an entire word, you can do that with this code:
p string =~ /quick/
The output of this will be 4 because the word quick begins at position 4.
A more practical example would be to check whether a letter, say z, is present in a string. If it's present, then it's a valid string; otherwise...