Variables are used to store data, while the program is running.
Regular variables as strings, numbers, real numbers and booleans, are called scalar variables.

Here are some scalar variables declarations:
name 'Tony'
age 22
height 176.80
isstudent \t
Tyl scalar variables features:

Tyl has also list variables, that can store a list of items.

Consider these list variables declarations:
names 'Tony' 'Carla' 'Ron'
data [ 22 28 17 ]
Tyl list variables features:
While it is common to declare a variable and assign a value to it in the same line, Tyl permits variable declaration without value assignment.

In this code:
prices variable will be defined as a list without items, and sumtotal variable will have undefined type, which is considered NULL.
Attention: The token 's' is also a list variable!

For more Information about variables: