beta perl

perl.html.markdown

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+---
+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