This document is an overview of Perl, a programming language designed primarily for text processing. It outlines Perl's features, syntax, data types, and operators, as well as basic programming constructs such as loops and conditionals. Additionally, it provides examples of file handling, regular expressions, and subroutine definitions, highlighting various components essential for coding in Perl.

1. P E R L
made by B Chari K working in semiconductors domain

2. What is PERL
 PERL stands for Practical Extraction and Report
Language.
 PERL is a programming language specially
designed for text processing
 Can be used for system administration, web
development, network programming, GUI
development, and more.
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3. PERL Features
 Perl takes the best features from other languages,
such as C, sh, and BASIC, among others.
 Perl supports both procedural and object-oriented
programming.
 Perl is an interpreted language.
 Perl program, first compiled into byte code, which
then compiled to machine instructions
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4. PERL Basics
 Can make perl files self executable by making
first line as #! /bin/perl.
 Perl files must be saved with .pl or .PL
 All commands have to end with “;”
 Pound sign ‘#’ is the symbol for comment entry
 There is no multi line comment entry in perl
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5. PERL Basics
 Whitespaces
 Perl doesn’t care about
whitespaces
 Single and Double
quotes
 Only double quotes
interpolate variables and
special characters
 But single single quotes
does not interpolate
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6. PERL Basics
 Print command used
to print any thing in
between double quotes
or single quotes
 Perl uses Backslash
character to escape
any meta character to
print
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7. HERE Documents
 Can store or print
multiline text with the
‘here’ document
 Can make use of
variables inside ‘here’
document
 $var = <<“EOF”
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8. Variables
 To store the values there are three types of
variables
 Scalar variable preceded by sign “ $ “
 Array variable preceded by “ @ “
 Hash variable preceded by “ % “
 Can store integers, decimals, or strings in these
variables.
 Can use the same name for scalar, array, hash.
 $foo and @foo are different variables
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9. Scalar ($)
 Scalar is a single unit
of data.
 $str = “string”;
 Can do scalar
arithmatic operations
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10. Scalar Operations

11. Array (@)
 Stores an ordered list
of scalar values
 @arr =
(“one”,”two”,”three”)
 The index starts from
zero.
 To refer single element
of an array, will use $
with the varialble
name.
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12. Sequential Number Arrays
 (..) is a range operator
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13. Add/Remove elements in array

14. Slice and Replace array elements
 Can extract an
elements from an array
 Splice() function removes
the elements, replace them
with list
 splice [@array, offset [ ,
length [ , list ] ]

15. Split() and Join functions
 split [ pattern [ , expr [ ,
limit ] ] ]
 Join expr, list

16. Hash ( % )
 Hashes are like arrays
 Hash preceded by “%”
 To refer to a single element
of a hash, hash variable
name preceded by a "$"
followed by the "key"
associated with the value in
curly brackets
 A hash is a set
of key/value pairs
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17. Extracting Keys and Values
 Can get a list of keys
using ‘keys’ function
 Keys = %HASH
 Can get a values using
‘values’ function
 Values = %HASH
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18. Add and remove elements in Hash

19. Getting User input
 Ex:
 $input = <STDIN>
 Print “you entered :
$input”
 STDIN accepts the
input from keyboard
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20.  If
 If..else
 If..elseif..else
 Unless
 Unless..else
 Unless..elsif..else
 switch
Conditional Statements
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21. Conditional Statements
 If (boolean_expression) {
# statement(s) will execute if the given condition is true
} else {
# statement(s) will execute if the given condition is false
}
 Unless (boolean_expression) {
# statement(s) will execute if the given condition is false
} else {
# statement(s) will execute if the given condition is true
}
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22. Example : Conditional
 If..else
 $a = 100;
if ( $a < 20 ) {
printf "a is less than 20n";
else {
printf "a is greater than
20n";
}
print "value of a is : $an";
 Unless..else
 $a = 100;
unless ($a == 20 ) {
printf "given condition is
falsen";
} else {
printf "given condition is
truen";
}
print "value of a is : $an";
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23. Loops
 While
 Until
 For
 Foreach
 do..while
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24. Example : loops
 While
 Syntax
 while(condition) {
statement(s); }
 Example
 $a = 10;
while( $a < 20 ){
printf "Value of a: $an";
$a = $a + 1; }
 Until
 Syntax
 until(condition) {
statement(s); }
 Example
 $a = 5;
until( $a > 10 ) {
printf "Value of a: $an";
$a = $a + 1; }
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25. Example : loops
 For Loop
 Syntax
 for ( init; condition;
increment ){ statement(s); }
 Example
 for( $a = 10; $a < 20; $a
= $a + 1 ){
print "value of a: $an"; }
 Foreach
 Syntax
 foreach var (list) { ... }
 Example
 @list = (2, 20, 30, 40, 50);
foreach $a (@list){
print "value of a: $an"; }
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26. define and call a Subroutine
 To define a subroutine
 sub subroutine_name{
body of the subroutine }
 To call a subroutine
 subroutine_name( list of
arguments );
 Example
 # Function definition
sub Hello{
print "Hello, World!n"; }
# Function call
Hello();
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27. Passing Arguments to subroutine
 #!/usr/bin/perl
# Function definition
sub Average{
# get total number of arguments passed.
$n = scalar(@_);
$sum = 0;
foreach $item (@_){
$sum += $item; }
$average = $sum / $n;
return $average;
print "Average for the given numbers :
$averagen"; }
# Function call
Average(10, 20, 30);
 The arguments accessed
inside the function using
“@_”
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28. Passing lists to subroutines
 #!/usr/bin/perl
# Function definition
sub PrintList{
my @list = @_;
print "Given list is @listn";
}
$a = 10;
@b = (1, 2, 3, 4);
# Function call with list parameter
Print list($a, @b);
 The my operator confines
a variable to a particular
region of code
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29. Operators
 Arithmatic Operators
 Numeric Equality Operators
 String Equality Operators
 Assignment Operators
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30. Arithmatic Operators
 $c = $a + $b
 $c = $a - $b
 $c = $a * $b
 $c = $a / $b
 $c = $a % $b
 $c = $a ** $b
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31. Numeric Equality Operators
 If ( $a == $b ) { … }
 If ( $a != $b ) { … }
 $c = $a <=> $b
 If ( $a > $b ) { … }
 If ( $a >= $b ) { … }
 If ( $a < $b ) { … }
 If ( $a <= $b ) { … }
 == Equal
 =! Not equal
 <=> returns -1 0 1 if
less than, equal, greater
than
 > Greater than
 < Less than
 >= greater than or
equal
 <= less than or equal
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32. String Equality Operators
 if( $a lt $b ) { … }
 if( $a gt $b) { … }
 if( $a le $b ) { … }
 if( $a ge $b ) { … }
 if( $a ne $b ) { … }
 Lt less than
 Gt greater than
 Le less than or equal
 Ge greater than or
equal
 Ne not equal
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33. Assignment Operators
Operator Example
= (simple assignment) $c = $a + $b will assigned value of $a +
$b into $c
+= (Add and assignment) $c += $a is equivalent to $c = $c + $a
-= (Subtract and assignment) $c -= $a is equivalent to $c = $c - $a
*= (Multiply and assignment) $c *= $a is equivalent to $c = $c * $a
/= (Divide and assignment) $c /= $a is equivalent to $c = $c / $a
%= (Modulus and assignment) $c %= $a is equivalent to $c = $c % a
**= (Exponent and assignment) $c **= $a is equivalent to $c = $c ** $a
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34. File Handle
 An internal Perl structure that associates a physical
file with a name.
 Basic File handles are
 STDIN
 STDOUT
 STDERR
 File handles are capable for read/write access
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35. Opening and Closing Files
 Open Function
 open FILEHANDLE, EXPR
 Ex:
 open(DATA, "<file.txt");
 open(DATA, "+<file.txt");
 open DATA, "+>file.txt“
 open(DATA,">>file.txt")
 open(DATA,"+>>file.txt“
 Close Function
 close FILEHANDLE
Entity Definition
< or r Read
> or w Create, write, truncate
>> or a Writes, appends, creates
+< or r+ Reads and writes
+> or
w+
Reads, writes and truncates
+>> or
a+
Reads, writes appends and
creates
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36. Reading and Writing Files
 $name = <DATA>
 Returns a single line from the file.
 @lines = <DATA>
 Returns a list of lines from handle.
 getc <STDIN>
 Returns a single characters
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37. Copying Files
 open(DATA1, "<file1.txt");
open(DATA2, ">file2.txt");
while(<DATA1>) {
print DATA2 $_;
}
close( DATA1 );
close( DATA2 );
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38. Rename and Delete files
 Rename the files
 rename (“/usr/test/file1.txt", “usr/test/file2.txt" );
 Delete the files
 unlink ("/usr/test/file1.txt");
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39. Directories
 Display files
 $dir = "/dir/*";
@files = glob( $dir );
print “@files”;
 Creates New directory
 $dir = "/dir1/perl";
mkdir( $dir )
 Removes a directory
 $dir = "/dir1/perl";
rmdir( $dir )
 Changes a directory
 $dir = "/dir1/perl";
rmdir( $dir )
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40. Special Variables
Variable Description
$_ Reading single line from a file
$0 Name of the file currently being used.
$[ Index of the first element in the array.
$] Version of perl being used.
@_ All the parameters passed from subroutine.
@ARGV Command line arguments passed to the program
$< User id of the process
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41. Regular Expressions
 Binding Operators ( ~= )
 Match Regular Expressions ( m// )
 Substitute Regular Expressions ( s ///)
 Translation Regular Expressions ( tr /// )
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42. Match Operator, ( m// )
 m/pattern/igxo
 Ex:
 $bar = "This is you and again
you";
if ($bar =~ /you/i ) {
print "matchingn";
} else {
print "not matchingn"; }
Modifier Description
i Match case insensitive
g Globally finds all matches
x Allows whitespace in
expression
o Evaluates expression only
once
 used to match a string or statement to a regular
expression.
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43. Regular Expression variables
Variable Description
$ Contains last group match
$& Entire match
$` everything before matched
$’ Everything after matched
 Ex:
 $string = “This is you and again you";
$string =~ m/you/;
print "Before: $`n";
print "Matched: $&n";
print "After: $'n";
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44. Substitution Operator ( s/// )
 Allows to replace the text matched with the new
text.
 Ex:
 $string = “This is you and
again you";
$string =~ s/you/me/;
print "$stringn";
Modifier Description
i Match case insensitive
g Globally finds all matches
x Allows whitespace in
expression
o Evaluates expression only
once
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45. Translation Operator ( tr/// )
 Tr/searchlist/replacementlist/cds
 Ex:
 $string = ‘this is me and again
me';
 $string =~ tr/m/h/;
 print "$stringn";
Modifier Descriptions
c Complements search list
d Deletes found but
unreplaced characters
s Squashes duplicate replaced
characters
 Replaces all occurances of characters in search list with
the corresponding characters in replacement list
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46. made by B Chari K