This slideshow was presented at Frozen Perl 2008 and covers a small portion of CPAN that any Perl programmer should be familiar with.

1. josh mcadams
doubleclick/performics

2. use strict;

3. use strict;
$perl = 'frozen';
$ref = 'perl';
print $$ref, quot;nquot;;
$ perl strict_refs.pl
frozen

4. use strict;
use strict quot;refsquot;;
$perl = 'frozen';
$ref = 'perl';
print $$ref, quot;nquot;;
$ perl strict_refs.pl
Can't use string (quot;perlquot;) as a SCALAR ref while quot;strict refsquot; in use
at strict_refs.pl line 4.

5. use strict;
use strict quot;varsquot;;
$perl = 'frozen';
$ref = 'perl';
print $$ref, quot;nquot;;
$ perl strict_vars.pl
Global symbol quot;$perlquot; requires explicit package name at strict_vars.pl line 2.
Global symbol quot;$refquot; requires explicit package name at strict_vars.pl line 3.
Global symbol quot;$refquot; requires explicit package name at strict_vars.pl line 4.
Execution of strict_vars.pl aborted due to compilation errors.

6. use strict;
use strict quot;varsquot;;
our $perl = 'frozen';
my $ref = 'perl';
print $$ref, quot;nquot;;
$ perl strict_vars.pl
frozen

7. use strict;
use strict quot;subsquot;;
$person = Josh;
$directory{mcadams} = [ first => $person ];
print $directory{mcadams}->[1], quot;nquot;;
$ perl strict_subs.pl
Bareword quot;Joshquot; not allowed while quot;strict subsquot; in use at
strict_subs.pl line 2.
Execution of strict_subs.pl aborted due to compilation errors.

8. use strict;
use strict quot;subsquot;;
$person = ‘Josh’;
$directory{mcadams} = [ first => $person ];
print $directory{mcadams}->[1], quot;nquot;;
$ perl strict_subs.pl
Josh

9. use strict;
- Typically ‘use strict;’ is all that you’ll need
- You can ‘no strict “refs”;’ in your code
- Use the strict pragma in all of your Perl code

10. use warnings;

11. use warnings;
perl -w script.pl
#/usr/bin/perl -w

12. use warnings;
use warnings;
no warnings;

13. use base;

14. use base;
push @ISA, ‘SomeModule’;

15. use base;
use base qw(SomeModule);

16. use constant;

17. use constant;
use warnings;
use strict;
use constant DO_NOT_DISTURB => 1;
print quot;leave me alonenquot; if DO_NOT_DISTURB;
> perl constant.pl
leave me alone

18. use Exporter;

19. use Exporter;
use MyPackage;
MyPackage::my_subroutine();

20. use Exporter;
package MyPackage;
use warnings;
use strict;
use Exporter qw(import);
our @EXPORT_OK = qw(my_subroutine);
sub my_subroutine {
print quot;hellonquot;;
}
1;

21. use Exporter;
use warnings;
use strict;
use MyPackage qw(my_subroutine);
my_subroutine();

22. use Data::Dumper;

23. use Data::Dumper;
use warnings;
use strict;
use Data::Dumper;
print Dumper @ARGV;
> perl datadumper.pl hello frozen perl
$VAR1 = [
'hello',
'frozen',
'perl'
];

24. use Class::Accessor;

25. use Class::Accessor;
sub name {
my ($self, $value) = @_;
$self->{name} = $value if $value;
return $self->{name};
}

26. use Class::Accessor;
package MyClass;
use base qw(Class::Accessor);
__PACKAGE__->mk_accessors(qw(name));

27. use Carp;

28. use Carp;
1 package PackageOne;
2
3 sub y { z(); }
4 sub z { die('oops'); }
5
6 package PackageTwo;
$ perl die.pl
7
oops at die.pl line 4.
8 sub a { b(); }
9 sub b { PackageOne::y(); }
10
11 package main;
12
13 PackageTwo::a();

29. use Carp;
1 package PackageOne;
2
3 use Carp;
4
5 sub y { z(); }
6 sub z { croak('oops'); }
7
$ perl croak.pl
8 package PackageTwo; oops at croak.pl line 11
9
10 sub a { b(); }
11 sub b { PackageOne::y(); }
12
13 package main;
14
15 PackageTwo::a();

30. use Carp;
1 package PackageOne;
2
3 use Carp qw(confess);
4 $ perl confess.pl
5 sub y { z(); } oops at confess.pl line 6
6 sub z { confess('oops'); } PackageOne::z() called at
7 confess.pl line 5
PackageOne::y() called at
8 package PackageTwo; confess.pl line 11
9 PackageTwo::b() called at
10 sub a { b(); } confess.pl line 10
11 sub b { PackageOne::y(); } PackageTwo::a() called at
12 confess.pl line 15
13 package main;
14
15 PackageTwo::a();

31. use Carp;
caller’s
standard full stacktrace
perspective
warn carp cluck
die croak confess

32. use Carp::Assert;

33. use Carp::Assert;
use Carp::Assert;
assert( 1 > 0 );
affirm {
my $name = 'Josh';
my @attendees = qw( Josh Heather Addy );
grep { $_ eq $name } @attendees;
}
> perl assert.pl

34. use Carp::Assert;
use Carp::Assert;
assert( 1 > 2);
affirm {
my $name = 'Josh';
my @attendees = qw( Josh Heather Addy );
grep { $_ eq $name } @attendees;
}
> perl assert.pl
Assertion failed!
at /opt/local/lib/perl5/site_perl/5.8.8/Carp/Assert.pm line 281
Carp::Assert::assert('') called at assert.pl line 5

35. use Carp::Assert;
use Carp::Assert;
assert( 1 > 0);
affirm {
my $name = 'Joshua';
my @attendees = qw( Josh Heather Addy );
grep { $_ eq $name } @attendees;
}
> perl assert.pl
Assertion ({
use warnings;
use strict 'refs';
my $name = 'Joshua';
my(@attendees) = ('Josh', 'Heather', 'Addy');
grep {$_ eq $name;} @attendees;
}) failed!
at /opt/local/lib/perl5/site_perl/5.8.8/Carp/Assert.pm line 340
Carp::Assert::affirm('CODE(0x1800ee0)') called at assert.pl line 11

36. use File::Spec;

37. use File::Spec;
use warnings;
use strict;
use File::Spec;
my @dirs = File::Spec->splitdir($0);
print '[', join('][', @dirs), quot;]nquot;;
my $dir = File::Spec->join(@dirs);
print $dir, quot;nquot;;
> perl /Users/joshua/examples/filespec.pl
[][Users][joshua][examples][filespec.pl]
/Users/joshua/examples/filespec.pl

38. use File::stat;

39. use File::stat;
my ($dev,$ino,$mode,$nlink,$uid,
$gid,$rdev,$size,$atime,$mtime,
$ctime,$blksize,$blocks) = stat
($filename);

40. use File::stat;
use warnings;
use strict;
use File::stat;
my $s = stat($0);
print $s->size, quot;nquot;;
> perl filestat.pl
84

41. use File::Slurp;

42. use File::Slurp;
{
local(*INPUT, $/);
open (INPUT, $file)
|| die quot;can't open $file: $!quot;;
$var = <INPUT>;
}

43. use File::Slurp;
my $text = read_file( $file );
my @lines = read_file( $file );

44. use File::Slurp;
write_file( $filename, @data );

45. use File::Copy;

46. use File::Copy;
use warnings;
use strict;
use File::Copy;
my $command = quot;cp $0 $0.bkupquot;;
`$command`;

47. use File::Copy;
use warnings;
use strict;
use File::Copy;
copy $0, $0 . '.bkup' or die $!;

48. use File::Temp;

49. use File::Temp;
use warnings;
use strict;
use File::Temp;
my $fh = File::Temp->new( UNLINK => 1 );
print $fh->filename, quot;nquot;;
> perl tempfile.pl
/tmp/yZin81tl6z

50. use File::Temp;
use warnings;
use strict;
use File::Temp;
my $fh = File::Temp->newdir( CLEANUP => 1 );
print $fh->dirname, quot;nquot;;
> perl tempdir.pl
/tmp/HggvehyAyw

51. use File::Find;

52. use File::Find;
use warnings;
use strict;
use File::Find;
find( sub { print quot;$File::Find::namenquot; },
'/Users/joshua/' );
> perl filefind.pl
/Users/joshua/...

53. use File::Next;

54. use File::Next;
use warnings;
use strict;
use File::Next;
my $files = File::Next::files( '/Users/joshua/' );
while ( defined ( my $file = $files->() ) ) {
print quot;$filenquot;;
}
> perl filenext.pl
/Users/joshua/...

55. use File::Basename;

56. use File::Basename;
use warnings;
use strict;
use File::Basename;
my $file = basename $0;
my $path = dirname $0;
my ($file2, $path2) = fileparse $0;
print join(quot;nquot;, $file, $path,
$file2, $path2), quot;nquot;;
> perl /Users/joshua/examples/basename.pl
basename.pl
/Users/joshua/examples
basename.pl
/Users/joshua/examples/

57. use File::HomeDir;

58. use File::HomeDir;
use warnings;
use strict;
use File::HomeDir;
print File::HomeDir->my_home(), quot;nquot;;
print File::HomeDir->my_data(), quot;nquot;;
> perl filehomedir.pl
/Users/joshua
/Users/joshua/Library/Application Support

59. use IO::File;

60. use IO::File;
use warnings;
use strict;
my $fh;
open( $fh, '<', $0 ) or die $!;
print while(<$fh>);
close $fh;

61. use IO::File;
use warnings;
use strict;
use IO::File;
my $fh = IO::File->new( $0, 'r' );
print while(<$fh>);
$fh->close;

62. use FindBin;

63. use FindBin;
package MyModule;
use warnings;
use strict;
sub hello {
print quot;hellonquot;;
}
1;

64. use FindBin;
use warnings;
use strict;
use lib 'mylib';
use MyModule;
MyModule::hello();
> perl findbin.pl
hello

65. use FindBin;
> perl ~/bin/findbin.pl
Can't locate MyModule.pm in @INC (@INC contains: mylib /
opt/local/lib/perl5/5.8.8/darwin-2level /opt/local/lib/
perl5/5.8.8 /opt/local/lib/perl5/site_perl/5.8.8/
darwin-2level /opt/local/lib/perl5/site_perl/5.8.8 /opt/
local/lib/perl5/site_perl /opt/local/lib/perl5/
vendor_perl/5.8.8/darwin-2level /opt/local/lib/perl5/
vendor_perl/5.8.8 /opt/local/lib/perl5/vendor_perl .) at
Utility Modules That You Should Know About/findbin.pl line
4.
BEGIN failed--compilation aborted at Utility Modules That
You Should Know About/findbin.pl line 4.

66. use FindBin;
use warnings;
use strict;
use FindBin;
use lib quot;$FindBin::Bin/../mylibquot;;
use MyModule;
MyModule::hello();

67. use Getopt::Long;

68. use Getopt::Long;
use Getopt::Long;
GetOptions(
'greeting=s',
'person=s',
'prefix:s' ) or die('error');
print join( q[ ],
$opt_greeting,
($opt_prefix || q[]),
$opt_person), quot;nquot;;
> perl getopt1.pl --greeting=hello --person=josh --prefix=
hello josh

69. use Getopt::Long;
use warnings;
use strict;
use Getopt::Long;
my ($greeting, $person, $prefix);
GetOptions(
'greeting=s' => $greeting,
'person=s' => $person,
'prefix:s' => $prefix,
) or die('error');
print join( q[ ],
$greeting,
($prefix || q[]),
$person), quot;nquot;;

70. use Getopt::Long;
use warnings;
use strict;
use Getopt::Long;
my %options;
GetOptions( %options,
'greeting=s',
'person=s',
'prefix:s',
) or die('error');
print join( q[ ],
@options{
qw(greeting prefix person)
} ),
quot;nquot;;

71. use Pod::Usage;

72. use Pod::Usage;
use Getopt::Long;
use Pod::Usage;
GetOptions('help', 'man') or pod2usage(2);
pod2usage(1) if $opt_help;
pod2usage(-verbose => 2) if $opt_man;
__END__

73. use Pod::Usage;
=head1 NAME
sample - Using GetOpt::Long and Pod::Usage
=head1 SYNOPSIS
sample [options]
Options:
-help brief help message
-man full documentation
=head1 OPTIONS
=over 8
=item B<-help>
Print a brief help message and exits.
=item B<-man>
Prints the manual page and exits.
=back
=head1 DESCRIPTION
Sample is exactly that, a sample.
=cut

74. use Pod::Usage;
> perl pod_usage.pl -h
Usage:
pod_usage [options]
Options:
-help brief help message
-man full documentation
Options:
-help Print a brief help message and exits.
-man Prints the manual page and exits.

75. use Pod::Usage;
> perl pod_usage.pl -m
POD_USAGE(1) User Contributed Perl Documentation POD_USAGE(1)
NAME
pod_usage - Using GetOpt::Long and Pod::Usage
SYNOPSIS
pod_usage [options]
Options:
-help brief help message
-man full documentation
OPTIONS
-help Print a brief help message and exits.
-man Prints the manual page and exits.
DESCRIPTION
pod_usage just an example.
perl v5.8.8 2008-02-16 POD_USAGE(1)

76. thank you

77. yapc.org/America