mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-27 09:15:50 +03:00
119 lines
3.1 KiB
Markdown
119 lines
3.1 KiB
Markdown
---
|
|
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.
|
|
|
|
|
|
#### 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
|