This document summarizes Brian D Foy's presentation on "My Perl Bag of Tricks" given at YAPC::Brasil 2011. Some of the tricks discussed include eliminating special cases, using Perl to do more of the work, scaling code gracefully, parsing XML data efficiently, testing code with sample inputs/outputs, and handling errors gracefully. The presentation aims to show Perl techniques for writing cleaner, more robust code.

1. My Perl
Bag of Tricks
brian d foy
The Perl Review
YAPC::Brasil 2011
http://slidesha.re/s06nuv

5. ⃠

6. • Eliminate special cases
• Remove distractions
• Know less
• Let Perl do the work
• Scale gracefully

7. % perl -e "print qq(Alo Mundon)"
% perl -le "print q(Alo Mundo)"

8. my $string = some_sub();
open my $fh, '<', $string;
while(<$fh>){
chomp;
...;
}

9. use 5.014;
my $new = $old =~ s/.../.../r;
foo( $old =~ s/.../.../r );
print "%s %sn",
$old,
$old =~ s/.../.../r
;

10. foreach my $file ( @files ) {
open my($fh), '>', $file or do {
warn "... $!n";
next FILE;
};
...
}

11. my $data = do {
local $/; <DATA>
};
...;
__END__
<?xml version="1.0"?>
<root>
...
</root>

12. my $data = do { local $/; <DATA> };
s|.*(?=<elem>)||; s|(?<=</elem>).*||;
my $name =
m|<elem>(.*?)</elem>|;
__END__
<?xml version="1.0"?>
<root>
...<elem>Buster</elem>
</root>

13. $g =
q("Mimi","Bean,Buster","Roscoe");
my @gatos = split /(?<="),(?=")/, $g;

14. $g =
q("Roscoe "","" Cat","Bean, Buster");
my @gatos =
split
/(?<!"")(?<="),(?=")(?!"")/, $g;

15. if( ref $r eq 'ARRAY' )
if( ref $r eq ref [] )
if( ref $r eq ref {} )
if( ref $r eq ref sub {} )
if( ref $r eq ref qr// )

16. join "n", @entries, '';
join "nt", "t", @entries;

17. BEGIN {
use Foo;
package Foo;
no warnings qw(redefine);
sub foo { ... }
}

18. # Git::CPAN::Patch
% git cpan-init http://...
... hack hack hack ...
% git commit
% git cpan-sendpatch

19. my $file = MPEG::Info->new( ... );
print
join $/,
map {
$file->$_()
} qw(acodec
acodecraw
achans
...
);

20. package Modulino {
run(@ARGV) unless caller;
sub run {
my @args = @_;
...;
}
}

21. if( /p{IsUppercaseRoman}/ ) {
...}
# ⅠⅤⅩⅬⅭⅮⅯↁↂↇↈ
sub IsUppercaseRoman {
return <<"CODE_NUMBERS";
2160
2164
2169
216C 216F
2181 2182
2187 2188
CODE_NUMBERS
}

22. printf
'%1$#b %1$#o %1$d %1$#xn",
137;
# 0b10001001 0211 137 0x89

23. gato( nome => 'Buster' );
sub gato {
my %defaults = (...);
my %config = (%defaults, @_ );
...;
}

24. BEGIN {
my $fixed_time = 1234567890;
no warnings qw(redefine);
*CORE::GLOBAL::time =
sub { $fixed_time };
sub set_time {
$fixed_time = $_[0]
}
}
ok( time > $fixed_time );

25. sub my_grep (&@) {
my( $sub ) = shift;
foreach my $arg ( @_ ) {
local $_ = $arg;
push @output, $arg
if $sub->()
}
}

26. my $ucfirst_and_trim =
composer(
&trim_front,
&trim_back,
&my_ucfirst
);
$s = $ucfirst_and_trim->($s);

27. sub composer {
my (@sub_refs) = @_;
sub {
my $string = shift;
foreach my $sub_ref (@sub_refs) {
$string = $sub_ref->($string);
}
return $string;
};
}

28. my @tests = (
# ARG EXPECTED LABEL
[ [1,2,3], 6, 'Sum is 6' ],
[ [-1,0,9], 8, 'Sum is 8' ],
...
);
foreach my $test ( @tests ) {
is(
target_sub( $test->[ARG] ),
$test->[EXPECTED],
$test->[LABEL]
);
}

29. package Local::Null::Logger {
sub new { bless my $x, $_[0] }
sub AUTOLOAD { shift; print @_, $/ }
sub DESTROY { 1 }
}
sub _init_logger {
my $log4perl_loaded =
eval "require Log::Log4perl; 1";
unless( $log4perl_loaded ){
return Local::Null::Logger->new;
}
...;
}

30. $object->foo->bar->baz->quux;
package Class {
sub bar {
return Null->new if $error;
}
}
package Null {
my $null = bless {}, __PACKAGE__;
sub new { $null }
sub AUTOLOAD { return $_[0] }
sub DESTROY { 1 }
}

31. Obrigado
http://slidesha.re/s06nuv

32. http://commons.wikimedia.org/wiki/File:Pelé_jump_1958.jpg
http://commons.wikimedia.org/wiki/File:Brazilian_National_Congress.jpg