The Perl Tutorial: What's Perl? (3)

Operators

Perl supports the same set of operators as most other computer languages. Operators allow a computer language to perform actions on operands. As in every computer language, Perl operators also have a certain precedence.

We've already encountered the assignment operator (=). This operator assigns a value from one variable to another:

$string1 = $string2;

The above code assigns the value of $string2 to $string1. We will now consider binary and unary arithmatic operators.

• 
  op1 + op2 The addition operator will add two numbers.
• 
  op1 - op2 The subtraction operator will subtract two numbers.
• 
  op1 * op2 The multiplication operator will multiply two numbers.
• 
  op1 / op2 The division operator will divide two numbers.
• 
  op1 % op2 The modulus operator will return the remainder of the division of two integer operands.
• 
  op1 xx op2 The exponentiation operator will raise op1 to the power of op2.
• 
  ++op1 The pre-increpment operator will increase the value of op1 first, then assign it.
• 
  op1++ The post-increment operator will increase the value of op1 after it is assigned.
• 
  --op1 The pre-decrement operator will decrease the value of op1 before it is assigned.
• 
  op1-- The post-decrement operator will decrease the value of op1 after it is assigned.

The logical operators are used mainly to control the flow of the program. Some of the logical operators that Perl supports include:

• 
  && The AND operator takes two values, and will return true only if both values are true.
• 
  || The OR operator takes two values, and will return true only if at least one value is true.
• 
  ! The NOT operator will negate a value.
• 
  op1 == op2 The equals operator checks for the equality of two numerical values.
• 
  op1 != op2 This not-equals operator checks for the inequality of two numerical values.
• 
  op1 < op2 This numerical operator will return true if op1 is less than op2.
• 
  op1 > op2 This numerical operator will return true if op1 is greater than op2.
• 
  op1 <= op2 This numerical operator will return true if op1 is less than or equal to op2.
• 
  op1 >= op2 This numerical operator will return true if op1 is greater than or equal to op2
• 
  op1 <=> op2 This numerical operator will return -1 if op1 is less than op2, it will return 0 if they are equal, and it will return 1 if op2 is greater than op1.
• 
  op1 eq op2 This string operator will return true if the two strings are equal.
• 
  op1 ne op2 This string operator will return true if both strings are not equal.
• 
  op1 lt op2 This string operator will return true if op1 is less than op2.
• 
  op1 le op2 This string operator will return true if op1 is less than or equal to op2.
• 
  op1 gt op2 This string operator will return true if op1 is greater than op2.
• 
  op1 ge op2 This string operator will return true if op1 is greater than or equal to op2.
• 
  op1 cmp op2 This string operator functions in the same manner as the numerical <=> operator described above.

There are other operators which can also be used in Perl. We have the concatenation operator for strings (.):

$string1 . $string2

The above code will concatenate $string1 with $string2 to form a new string.

We also have the repetition operator (x), this operator will repeat a string a certain number of times specified:

$string1 x 2;

The above code will repeat $string1 twice.

The range operator allows us to use ranges, in arrays or patters:

@array = (1..50);

The above code will assign 50 elements to the array.

As we have already seen, we have a wide variety of operators that work with scalar values, but if we wanted to work with arrays we could do what is called "array splicing". Let's say we have an array with 10 values. If we want to assign values 5 and 6 to two scalar values we could do the following:

($one,$two) = @array[4,5]; #remember that arrays start at subscript 0.

In the above code we just spliced two values from the array. When we do array splicing we use the @ sign, followed by the array name, followed by brackets and the subscripts that you want separated by commas. So instead of having two lines for the above code we have one. We need to enclose the two scalar values in parentheses in order to group them

Functions