Beginning Web Development With Perl : From Novice to ... - Nabo

CHAPTER 12 ■ THE TEMPLATE TOOLKIT 245List variables are set by including the list of values within brackets, [ and ]:[% months = [jan,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec] %]■Note Commas are used to separate the values in the example, but they are not required. A space can beused just the same.These elements are accessed with dot notation, with the first index indicated by 0. Forexample, this code accesses the second element in the months list example just shown:[% month.1 %]Based on that earlier example, the value for [% month.1 %] is feb.While lists or arrays are indicated by brackets, [ and ], hashes are indicated by braces, {and }:[% months = {jan => 'January'feb => 'February'mar => 'March'apr => 'April'}%]Values belonging to the keys of the hash are accessed using the dot operator with hashvariables. For example, the following code accesses the value for the key named mar in theprevious example:[% months.mar %]The value contained in [% months.mar %] is March. You can also use multiple dot operatorsto create and retrieve arbitrarily long nested hashes.■Note Variables declared with a leading underscore (_) character are defined as private and will not beused outside the object’s methods.Whereas the variable types just explained are static, meaning they only return valuesexplicitly set or assigned to them, dynamic variables can be assigned to Perl subroutines andobjects, which will then process and return information to the variables for use in templateprocessing.Working with VariablesMathematical operations can also be performed on variables when they are being set orretrieved. This example adds the result of two dice being rolled: