// get all pets where the pet_name has an 'e' in the text.
db.pets.find(
    {
        pet_name: { $regex: 'e'}
    }
)

// count number of results
db.pets.find(
    {
        pet_name: { $regex: 'e'}
    }
).count()

// find all pets where pet_name has a capital 'E' right after a lowercase 'e'
// should not return any because there are no documents with 'eE' in the pet_name value.
db.pets.find(
    {
        pet_name: { $regex: 'eE'}
    }
)

// make it so capitalization differences don't affect the results.
// This is good to know because your users will be frustrated if a result doesn't show up due to capitalization errors.
// Imagine trying to find your friend "John" and can't because he put his name as "joHn".
db.pets.find(
    {
        pet_name: { $regex: 'eE', $options: 'i'}
    }
)