1. Karan Thaker CS 265 Section 001
Introduction to Perl
Karan Thaker
CS 265 Section 001

2. Topics Covered What is Perl? Scalar Data Variables and Operators
If-else and while control structures
Standard input
Lists and Arrays

3. What is Perl? Practical Extraction and Reporting Language
Very widely used SCRIPTING language
Designed for text processing
“There’s more than one way to do it”

4. Scalar Data Simplest type of data that PERL manipulates
Either a number or string
Can be acted upon with operators (like plus or concatenate)
Integers and floats have essentially the same format
“undef” – special value assigned to all variables
Zero when assigned to numbers
NULL when applied to strings

5. Variables and Operators
Naming:
Begins with “$” followed by the identifier
For example, $karan, $drexel, $computer
Any scalar variable holds
a SINGLE scalar value
Operators
Assignment =
Arithmetic
+ , - , * , /
String
-string concatenation (a dot),
x –string repetition
Numeric comparison
== , != , < , > , <= , >=
String comparison
eq, ne, lt, gt, le, ge

6. Control Structures if - else while Similar to C++
Curly braces required
if - else
while
if(...) {
...
}else ( }
if(...) {
... }
while(...) {
... }

7. Standard Input $line =<STDIN>;
Reads a full line from input and stores 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"; }
A line of input is read and one of the two strings is printed out
while(defined($line=<STDIN>)){
print “This line was: $line \n”; }
Input is displayed in output, and loop stops when end-of-file is reached.

8. Lists and Arrays Reading into a list Accessing list elements
(1,2,3,4,5,6,7,8,9,10) # list consisting of numbers 1 to 10
(1..10) # same list created by the range # operator
($a ..$b) # the range determined by current values of $a and $b
Reading into
a list
Accessing list
elements
@numbers=(1..100);
print $numbers[0]; # prints 1
print $numbers[10]; # prints 11
while(<>){
$lines[$index]=$_ ;
$index=$index+1; }
print $#lines+1;
List Assignment
($fred, $barney)=($barney, $fred); # values are swapped
@numbers=(1..10); # list (1..10) is stored inside an array

9. Thank you