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1Getting Started with Perl
2Getting Started with CGI
3Operators
4Flow Control
5Working with Scalars
6Working with Lists
7Working with Hashes
8Reading, Writing and Manipulating Files
9Pattern Matching
10Creating and Using Subroutines
11References
12Packaging and Modules
13Using the CGI.pm Module
14Retrieving Data with CGI
15CGI Script Debugging and Security

CGI Programming with Perl

Lesson 1: Getting Started with Perl

 TypeExample
$Scalar$name = "Gary Patterson";
@Array@colors = (red, green, blue);
%Hash%mfr("747") = "Boeing";
&Subroutine&display("Please wait...");
*Typeglob*filehandle;

WrongRight
#! /usr/bin/local/perl

$input = <STDIN>;

if ($input ne "") {
   print($input);
} else {
   print("no input");
}
 		#! /usr/bin/local/perl

$input = <STDIN>;

if ($input ne "\n") {
  print($input);
} else {
  print("no input");
}
Perl's <STDIN> from the keyboard appends a newline to the input. When testing for a keyboard empty line, use ($x eq "\n") instead of ($x eq ""). To avoid this, use the chomp($input); code.
#! /usr/bin/local/perl

@c=('red','green','blue');

for ($i=0; $i<@c; $i++) {
  print('$c[$i]\n');
}
 		#! /usr/bin/local/perl

@c=('red','green','blue');

for ($i=0; $i<@c; $i++) {
  print("$c[$i]\n");
}
Notice the double quotes in the print() command parameter. It forces the variables to be interpreted by reference instead of literals.

Exercises

1 perl -e "print(\"John Doe\n\")"; -e "print(\"123 Main St\n\")"; -e "print(\"Anytown, MA 12345\")";
perl -e "print qq(John Doe\n123 Main Street\nAnytown, USA 12345\n)"
2 print("Enter your Name: ");
$name = <STDIN>;
chomp($name);

if ($name eq "") {
  $name = "No name given";
}

print("Enter your Address: ");
$addr = <STDIN>;
chomp($addr);

if ($addr eq "") {
  $addr = "No address given";
}

print("Enter your City, State and Zip Code: ");
$CSZ = <STDIN>;
chomp($CSZ);

if ($CSZ eq "") {
  $CSZ = "No City, State, and Zip Code given";
}

print("$name\n$addr\n$CSZ\n");
3 $last = <STDIN>;
chomp($last);

$first = <STDIN>;
chomp($first);

$addr = <STDIN>;
chomp($addr);

$city = <STDIN>;
chomp($city);

$state = <STDIN>;
chomp($state);

$zip = <STDIN>;
chomp($zip);

print("$first $last\n");
print("$addr\n");
print("$city, $state $zip\n");

perl sourcefile.pl <datafile
4 $line = <STDIN>;
while ($line ne "") {
  print($line);
  $line = <STDIN>;
}

while ($line = <STDIN>) {
  print $line;
}

perl sourcefile.pl <inputfile >outputfile

 

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