Naming conventions

Perl 6 does not force the user to follow any specific naming conventions for variable names. Still, it is better to follow a general common sense approach. Variable names may be as short as one letter, but they can also be descriptive and contain many words.

Single-letter names are the best choice in loops, or in some calculations where all the mentions of the variable are located compactly and are clearly visible on the screen. Single-letter names, of course, may use both lower and uppercase letters. While there is no standard in Perl 6, the uppercase names are used for constants and pseudo-constants in the documentation; for example, check out https://docs.perl6.org/language/variables#Compile-time_variables.

Here are some examples of single-letter names:

constant $N = 100;
my $n = prompt('Enter a number: ');
say "You entered $n";
say 'This number is too big' if $n > $N;

For longer names, there are a few alternatives. Either you start with a small or capital letter, or the whole name is capitalized. Again, uppercase names such as $MAXIMUM are better to represent constants, even if you don't use the constant keyword. In general, lowercase names are preferable. Let's rewrite the previous program so that it uses longer variable names:

constant $MAXIMUM = 100;
my $value = prompt('Enter a number: ');
say "You entered $value";
say 'This number is too big' if $value > $MAXIMUM;

In many cases, even longer names are needed. In this case, there are a few ways to construct the name using two or more words. First, you can use the so-called camel case names, for example, $userValue or $valueFromInput. Second, the underscore character is a good candidate for concatenating parts of the name—$user_value or $value_from_input; this style is called snake case. Finally, Perl 6 allows extravagant names with dashes, for example, $user-value or $MAXIMUM-VALUE (kebab case). The - character is not a minus operator in this case, and is a part of the name. So, the $uservalue, $userValue, $user_value, and $user-value names are four different names. Consider the following code snippet:

constant $MAXIMUM-VALUE = 100;
my $entered-value = prompt('Enter a number: ');
say "You entered $entered-value";
say 'This number is too big'
    if $entered-value > $MAXIMUM-VALUE;