Introduction to Perl

Week 2
These are the topics that we shall cover during the second week. 

Why Perl?

• Interpretive language; no compilation no linking. Type-and-go!
• Power; speed
• Portability; runs on ANY platform; UNIX, Windows, Mac
• Popularity and hence extensive support library
• Cost

Hello world!

1. Logon to smb.ctp.bilkent.edu.tr (You should have obtained an account on this computer by now. If you have not yet done so, see Mr. Satuk Erculasun in the CTP systems room)
2. Use vi to enter the following code into a file (hello.pl) ( See "Just enough vi commands to survive" and the "vi tutorial" for some help on using the "vi" editor)

print "Hello world!\n";

3. Run your program with the command "perl ./hello.pl"
4. Modify the hello.pl file so that it contains the lines

#!/usr/bin/perl
print "Hello world\n";

5. Modify the access rights to allow execution by everyone (Hint : use the chmod command)
6. Run the new program with the command "./hello.pl"

Perl Variables

• Scalars : $var_name
• Arrays : @array_name

• Indexes start at 0
• Single elements are addressed as scalars (name starts with $) and index is given between [ ].

• Hashes : %hash_name

• Indexes can be anything; single elements are addressed as scalars (name starts with $) and index must be enclosed with { }.

Basic I/O

I/O From Standard I/O Devices  : 

print STDOUT, "text to print";
print "text to print";

$name = <STDIN>;
chomp($name);
print "You have entered $name\n";

Flow Control

• if  - else - elsif 
• while, last, next
• foreach
• function calls, return

Conversions

• String to numerics, numerics to strings
• Scalars to arrays
• Arrays to scalars