Perl is an open-source, cross-platform scripting language that is multi-paradigm and uses dynamic typing. It was created in 1987 and is popular for web programming using CGI scripts. Perl has scalars, arrays, hashes, and complex data types like references that allow it to represent complex data structures. It supports common programming constructs like conditionals, loops, subroutines, pattern matching and more.

1. Perl 簡介 Sway 2010/12/28

2. equals( , ) Cross-platform, open-source, scripting language, multi-paradigm, dynamic typing, statement ratio: 6 There should be one way There’s more than one way Guido van Rossum Larry Wall 1991 1987 Python Perl Easy Difficult

3. Perl 特色 while(<>){ chomp; print join(“\t”, (split /:/)[0, 2, 1, 5] ) , “\n”; } 如果用 C 寫 上面這段程式的大小會增長十幾倍

4. CPAN Comprehehensive Perl Archive Network http://www.cpan.org/ 中譯為「 Perl 綜合典藏網」 「 Perl 綜合檔案網」 3400+ authors 12000+ modules CPAN shell 快速安裝套件

5. you must be joking! http://www.strombergers.com/python/ my @list = ('a', 'b', 'c'); my %hash; $hash{‘letters'} = \@list; print &quot;@{$hash{‘letters'}}\n&quot;; list = ['a', 'b', 'c'] hash = {} hash[‘letters'] = list print hash[‘letters'] package Person; use strict; sub new { my $class = shift; my $age = shift or die &quot;Must pass age&quot;; my $rSelf = {'age' => $age}; bless ($rSelf, $class); return $rSelf; } class Person: def __init__(self, age): self.age = age @list = ( [‘a’, ’b’, ’c’], [1, 2, 3] ); print “@{$list[0]}\n”; list = [ [‘a’, ’b’, ’c’], [1, 2, 3] ] print list[0]

6. More Perl bashing… http://www.strombergers.com/python/ sub add { $_[0] + $_[1]; } def add(a, b): return a + b sub add { my ($a, $b) = _@; return $a + $b; } sub add { my $a = shift; my $b = shift; return $a + $b; } def diff(a, b): return len(a) - len(b) sub diff { my ($aref, $bref) = _@; my (@a) = @$aref; my (@b) = @$bref; return scalar(@a) + scalar(@b); } sub add($, $) { local ($a, $b) = _@; return $a + $b; }

7. More Perl…

8. CGI Perl is widely used for web programming

9. Perl Syntax Basic Script #!/usr/bin/perl $inputline = <STDIN>; print($inputline); Data Types Perl has three main variable types: scalars, arrays, and hashes dynamically typed.

10. one of ten Perl myths http://www.perl.com/pub/a/2000/01/10PerlMyths.html “… Perl works the way you do…” “… That's one, fairly natural way to think about it…” while (<>) { s/(.*):(.*)/$2:$1/; print; } Swap two sections of a string: “aaa:bbb” -> “bbb:aaa” for line in file: line = line.strip() first, second = line.split(‘:’) print second+’:’+first while (<>) { chomp; ($first, $second) = split /:/; print $second, &quot;:&quot;, $first, &quot;\n&quot;; } “… we can happily consign the idea that ‘Perl is hard’ to mythology.” from re import sub for line in file: print sub(‘(.*):(.*)’, r’\2:\1’, line)

11. Scalars A scalar represents a single value: string, integer or floating point numbers. automatic conversion. $string = &quot;hello&quot;; $color = ‘green’; $num = 88; $float = 9.58;

12. Arrays @animals = (“cat&quot;, “dog&quot;, “rabbit&quot;); @nums = (11, 22, 33); @mixed = (&quot;cat&quot;, 1.23);

13. Hashes A hash is a set of key/value pairs: - %ages = (“tom&quot;=>18,“jack&quot;=>21); - %same = (&quot;lee&quot;,18,“wang&quot;,21); - %mixed = (1=>“Mon&quot;, “pi&quot;=>3.14) - %empty_hash = ();

14. Complex data types Reference: A scalar value $scalarref = \$num; $arrayref = \@mixed; $hashref = \%ages;

15. Complex data types - A reference can refer to any other Perl data type: $table = { “jack” => { age => 47; id => “teacher”, }, “ peter” => { age => 21 id => “student”, }, “ tom” => { age => 59 id=> “retired”, }, };

16. Comparison Numeric / String == / eq equal != / ne not equal < / lt less than > / gt greater than <= / le less than or equal >= / ge greater than or equal

17. Pattern Matching . any character except newline \s white space (space, tab, newline...) \S non-white space \d any digit (0-9) \D any non-digit \w any word character (a-z, A-Z, 0-9, _) \W any non-word character [abcde] any single character within the set [^abcde] any single character outside the set | alternatives ^ beginning of string $ end of string * + ? { } number of occurrences () pattern memory

18. Conditional constructs if (cond ) { ... } if (cond ) { ... } else { ... } if (cond ) { ... } elsif (cond ) { ... } else { ... } Negated if statement: unless cond {…} post-condition {…} if (cond)

19. Conditional constructs

20. Looping constructs while (cond ) { ... } while (cond ) { ... } continue { ... } Negated while statement until (cond ) {…} post-condition of while {…} while (cond);

21. Looping constructs

22. Subroutines Call subroutine - subname(); &subname; - $cub = cubic(8); Example: sub cubic { my $num = shift; my $result = $num * $num * $num; return $result; } pass-by-value, pass-by-reference

23. Perl 6 http://www.perl6.org/