Perl why use my

So its function is to ensure the Perl version of the module invocation environment. Our, like my , is a declaration of variables. But our declares package global variables. My declares lexical variables.

However, with our declared variable, it becomes like a lexical variable. In fact, this is also our purpose: to deceive strict pragma and make strict think it is a lexical variable, but it is not. There is a simple way to understand our: 1. You treat our declared variable as my declared variable. Keep in mind the difference between our and my: our declaration is a package global variable, so it can be stored in the symbol table which can be accessed anywhere with full restriction , while my declaration is a real lexical variable that can only be accessed in closed blocks.

It is currently bound to the use of the fields pragma, and attributes are handled using the attributes pragma, or starting from Perl 5. See "Private Variables via my " in perlsub for details. If you want to declare global variables that are visible throughout your program or from external packages, you can use our keyword as shown in the following code:.

Perl interpolates variables in double-quoted strings. Note that Perl only interpolates scalar variables and arrays , not hashes.

In addition, the interpolation is only applied to the double-quoted string, but not the single-quoted string. In this tutorial, you have learned about Perl variables including naming and declaring scalar variables.

This variable can be accessed in any scripts which will use that package. This will help you write better and cleaner code. An Array is a special type of variable which stores data in the form of a list; each element can be accessed using the index number which will be unique for each and every element.

You can store numbers, strings, floating values, etc. This looks great, So how do we create an array in Perl? This is how we define an array in Perl; you might be thinking how we need to store data in it.

There are different ways of storing data in an array. This depends on how you are going to use it. The array index starts from 0 and ends to its maximum declared size, in this case, the max index size is 3. You can also declare an array in the above way; the only difference is, it stores data into an array considering a white space to be the delimiter. Here, qw means quote word. The significance of this function is to generate a list of words.

You can use the qw in multiple ways to declare an array. Suppose you want to assign a value to the 5 th element of an array, how are we going to do that. Sequential arrays are those where you store data sequentially. Suppose, you want to store numbers or alphabets a-z in an array. Instead of typing all the letters, you can try something like below —. The above method of declaring an array is called static arrays , where you know the size of an array.

Dynamic arrays are those that you declare without specifying any value on them. So when exactly do we store values in that array?

Simple, we store them during run time. Here is a simple program for that. The split function splits the content of string into an array based on the delimiter provided to it. What exactly arrays do? It is a collection of scalars, where you access each element of an array using indices. But, is this good idea to use an array when you have hundreds and thousands of records?

We will forget which index has what value. To overcome this situation we have something like perl hash. A hash can also hold as many scalars as the array can hold.

This way it is difficult to know individual ages as we need to remember both index locations of name and age of all the people. It may be simple when you have 3 names, but when you have or more?

You know the answer. We have now declared a hash, great!! But, how do we access or print it? Each element in hash should be accessed with its associated key for which there will be a value assigned. So, there is a one-one mapping between each of the key and value in the hash. Note: Each Key in hash should be unique or else it will override your value, which was assigned previously.

Delete is an inbuilt function of Perl. Here, we will see an example of assigning a hash to an array. Note: Whenever you print a hash or when you store hash into an array. The order may always differ. We can use conditional Statements in Perl. So, what are conditional statements?

Conditional statements are those, where you actually check for some circumstances to be satisfied in your code. So, the rule here is bucks. This way we can control only one condition at a time.

Is it a limitation? No, you can also control various conditions using if… elsif … else. There could be situations where both if and elsif code blocks will be failed. In this scenario, the else code block will be executed. You have already got an idea what if does If the condition is true it will execute the code block. Unless is opposite to if, unless code block will be executed if the condition is false. Guess what will be the output. You are right!!!!!. The output will be the print statement of the else block.

Because of the condition in unless code block is true, remember unless block will be executed only if the condition is false. Perl supports control structures similar to other programming languages. Perl supports four types of control structures for, foreach, while and until. We use these statements to, repeatedly execute some code. For code block will execute till the condition is satisfied. Here, in for expression, there are many statements included. There is a meaning for each of them. This looks good for accessing arrays.

How about Hashes, how can we obtain hash keys and values using foreach? You might be wondering, Why we used Keys in foreach. Keys is an inbuilt function of Perl where we can quickly access the keys of the hash. How about values? We can use values function for accessing values of the hash. The Perl While loop is a control structure, where the code block will be executed till the condition is true.

If you see how while works here, the code block will execute only if the condition in a while is true. Until code block is similar to unless in a conditional statement. Here, the code block will execute only if the condition in until block is false. Do until can be used only when we need a condition to be false, and it should be executed at-least once. Operators in computer language indicate an action that can be performed on some set of variables or values which computer can understand.

Perl has incorporated most of the Operators from C language. Perl has many operators compared with other programming languages. Operators are categorized as Arithmetic, Logical, relational and assignment operators.

Arithmetic operators are those which can be used to perform some basic mathematic operations. These Arithmetic operators are binary operators where we need two arguments to perform a basic operation. We can also use unary operators for other basic operations; you can see the difference in examples below. Modulus operator used to get the reminder during division of two values or variables holding values. Assignment operators simply assign values to variables, but there is one more thing which we need to remember here, assignment operators will also perform arithmetic operations and assign the new value to the same variable on which the operation is performed.

Modulus operator used for getting a reminder during division and assigning the value to the same variable. Perl uses logical operators to compare numbers and strings. Most of the time logical operators are used in Conditional Statements.

Special variables in Perl are those who have some predefined meaning. These variables denoted with either real Name or Punctuation symbols. We have a special variable for all the Perl supported Variables like scalar special variables, Array special variables, hash special variables.

Most of the special variables that we use are of scalars. Output field separator, this is mainly used by the print statement. By default value of this is set to 0, we can change the value of this variable. Output record separator, the value of this variable will be empty; we can assign any value to this, which will be used by print statement while printing the output.