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.
#### 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
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.
