---
name: perl
category: language
language: perl
filename: learnperl.pl
contributors:
    - ["Korjavin Ivan", "http://github.com/korjavin"]
---

Perl 5 is a highly capable, feature-rich programming language with over 25 years of development.

Perl 5 runs on over 100 platforms from portables to mainframes and is suitable for both rapid prototyping and large scale development projects.

```perl
# Single line comments start with a hash.

/*
Multi-line comments look like this.
*/


#### Perl variable types

#  Variables begin with the $ symbol.
#  A valid variable name starts with a letter or underscore,
#  followed by any number of letters, numbers, or underscores.

### Perl has three main variable types: scalars, arrays, and hashes.

## Scalars
#  A scalar represents a single value:
my $animal = "camel";
my $answer = 42;

# Scalar values can be strings, integers or floating point numbers, and Perl will automatically convert between them as required.

## Arrays
#  An array represents a list of values:
my @animals = ("camel", "llama", "owl");
my @numbers = (23, 42, 69);
my @mixed   = ("camel", 42, 1.23);



## Hashes
#   A hash represents a set of key/value pairs:

my %fruit_color = ("apple", "red", "banana", "yellow");

#  You can use whitespace and the "=>" operator to lay them out more nicely:

my %fruit_color = (
        apple  => "red",
        banana => "yellow",
        );
# Scalars, arrays and hashes are documented more fully in perldata. (perldoc perldata).

# More complex data types can be constructed using references, which allow you to build lists and hashes within lists and hashes.

#### Conditional and looping constructs

# Perl has most of the usual conditional and looping constructs.

if ( $var ) {
    ...
} elsif ( $var eq 'bar' ) {
    ...
} else {
    ...
}

unless ( condition ) {
                   ...
               }
# This is provided as a more readable version of "if (!condition)"

# the Perlish post-condition way
print "Yow!" if $zippy;
print "We have no bananas" unless $bananas;

#  while
  while ( condition ) {
                   ...
               }


# for and foreach
for ($i = 0; $i <= $max; $i++) {
                   ...
               }

foreach (@array) {
                   print "This element is $_\n";
               }


#### Regular expressions

# Perl's regular expression support is both broad and deep, and is the subject of lengthy documentation in perlrequick, perlretut, and elsewhere.  However, in short:

# Simple matching
if (/foo/)       { ... }  # true if $_ contains "foo"
if ($a =~ /foo/) { ... }  # true if $a contains "foo"

# Simple substitution

$a =~ s/foo/bar/;         # replaces foo with bar in $a
$a =~ s/foo/bar/g;        # replaces ALL INSTANCES of foo with bar in $a


```

#### Using Perl modules

# Perl modules provide a range of features to help you avoid reinventing the wheel, and can be downloaded from CPAN ( http://www.cpan.org/ ).  A number of popular modules are included with the Perl distribution itself.

# perlfaq contains questions and answers related to many common tasks, and often provides suggestions for good CPAN modules to use.

#### Further Reading

[Learn at www.perl.com](http://www.perl.org/learn.html)
 and perldoc perlintro