Part I

Introduction Scalar Data Variables Operators If-Else Control Structures While Control Structures Standard Input Lists and Arrays

Perl 1 - Created by Larry Wall in 1987 Stable Release: Perl 5.10.1

Two basic scalar data types: Numbers and Strings

Numbers

-Integers and Floating-Point Numbers have the same format.

Ex. $v=8      #v contains value of 8

Strings

-Sequences of Characters.-Can either be enclosed in single or double quotes.

Ex. $v=“a”      #v contains value of “a”

Undef –

For Numbers or Strings, there is a special value called undef. This is initially assigned to all variables and acts as a zero for numbers and a null or empty string for strings.

A scalar variable holds a single scalar value Names of any scalar variable must begin

with the “$” symbol followed by a Perl identifier

Ex. $tom, $cs265

Assignment Arithmetic String Numeric Comparison String Comparison

=Ex. $cs = 265

+, -, *, /Ex. $c = a + b (Addition)$c = a – b (Subtraction)

$c = a * b (Multiplication)$c = a / b (Division)

., x. (dot) – String Concatenation

Ex. $cl = class, $ro = room, $cl . $ro = classroom

x – String MultiplierEx. $cl x 2 = classclass

==, !=, <,>,<=,>=

eq, ne, lt, gt, le, ge

1. Interpolation of scalars into strings◦ Any scalar variable inside a double quoted string is

replaced by its value. ◦ Ex. $example=“example”; print "$example"; prints

example 2. Automatic conversion between numbers and

strings◦ Arguments of an arithmetic operator are automatically

recognized as numbers, and arguments of a string operator as strings.

◦ Ex. $one = 1, $two = 2..◦ print $one*$two; prints 2◦ print $one x $two; prints 11◦ print $one . $two prints 12

Conditional Loop

if(…){

… } else {

… }

$expected = “apple”; $given = “pear”;

if($expected eq $given){ print “Apple”

} else { print “Other Fruit”

}

Conditional Loop

while (…) { … }

$num = 1;while ($num != 1111) {

$num . $num;}

Input in Perl is very convenient <STDIN>

Ex. Typical Line of Code for input

$line=<STDIN> # read a full line from standard input and store it in variable $line

$line=<STDIN>; if($line eq "\n"){

print "This was an empty line.\n"; } else {

print "This line was not empty.\n"; }

Lists are also user friendly in Perl List Literals (representations of lists)

◦ Ex. (1,2,3,4) # a list consisting of numbers 1,2,.. 4◦ Ex. (1..10) # the same list as the one above, now

created by the range operator ($a ..$b) - the range determined by current values

of $a and $b List Assignment Examples:

Arrays are variables storing lists. @num = (1..100) # creates an array “num”

with a numbers 1 through 100◦ print $num[0] # prints out 1◦ print $num[$#num] # prints out the largest index

of the array