Perl Advanced Course


  • get Eclipse Epic module
  • ask for sw repository in cern


  • Access to values over $main::{name}
  • Or over *main::name

Two ways to adress variables:

  • my and local
  • gets stored in a diffrent way
  • local creates a temporary limited package based scalar, array, hash, or glob.
  • the previous value is restored
  • my variable creates a limited nonpackage-based scalar


Make a reference to another subroutine:

  • $d = \$prog

$$ptr= 20;
print $m; gives 20

change from array to scalar:
@mat; print @{$mat[0]}
this will show the topic, not the ARRAY hash

  • goto Active Perl User Guide for more info about references

Packages and Modules

  • The symbol __PACKAGE__ will return the package name
note: use bless for inheriting from other sub function

  • my doesnt store symbol vars, use global ISA


  • require: is in INC, requires a file containing perl code and compiles it
    • required module must have a true value do get compied
    • use eval statement to check if it is existing
  • use: uses functions with import, to import the real values of the scalars in modules.
    • if import function is not available use require
    • use newer than require

note: use exprot in grouplist to import it in isinlist!!!!!!!!

Global Variables

  • use vars qw
  • or our (scalars, hashes...)

Object Oriented Perl


  • The class is no more than a package
  • puts method definitions into class
  • using subroutines


  • a class is a description of the objects of the class
  • e.g today is an instance of class date

2 Types of methods:

  • class methods:
    • call the method
  • instance methods:
    • calls the functions of a method


2 Types of Variables:
  • Class variables
  • instance variables


a class provides one constructor. it is a reference to an associative array. it returns a blessed reference.
  • bless to transform a reference into an object


with DESTROY we can free used objects for new contstucting.
PERL does this automatically.


To use existing classes as a base of others. needs a new constructer, even when no new vars are needed.. bless (self, class) return self @ISA, UNIVERSAL, AUTOLOAD use this for inheriting


Using objects and instance variables

Operator Overloading

to substitute class methods or own subroutines for standard perl operators.

package Date<
use overload `==` => "equals", (name of method)
                    `<` => \&lowerthan; (reference to method)

all overloadable operators are in %overload::ops hash

Tied Variables

tie to create seemingly normal variable that is actually a full fledged Perl object.

binds variable to classname

$object = tied VARIABLE;



Databases and Perl

see course book

Taint mode

  • to validate input data
  • prevent traps
  • ARGV[0] & ENV{} is tainted
  • only the values in a hash can be tainted, not the keys

see page 78

untaint function

use IO::Handle;
open DATA, "data.log";
DATA->untaint();   #DATA is now untainted

open files secure

open (DATA, "<", "$file"); #safest solution

Make ENV secure


Reg EX advanced

note: page 85

REGEXP::COMMON module hass a lot of pre tested reg exps to use for

-- AlexanderBernegger - 10-Dec-2009

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