The Source_er’s Apprentice: Powerful Tips & Techniques in Perl you can start using today

1. The Source_er’s Apprentice:Powerful Tips & Techniques in Perl you can start using today Matthew Heusser xndev.com - matt@xndev.com Presented to the West Michigan Perl Mongrels – 8/25/2006

2. Techniques … there is a distinct difference between learning to use Perl, and learning to use it well. In my opinion, the best way to learn any language well is to see how others have used it to solve problems - Some Dude on Amazon.com

3. Velocity & Pinball skills

4. Trick #1:Use Parameters my $new = convert('616-555-1212'); print "New Number is $new\n"; sub convert { my $num = shift; $num=~s/^616-5/269-5/g; $num=~s/^616-31/269-31/g; $num=~s/^616-32/269-32/g; return $num; } _

5. Trick #2:Use Interpolation my $cash = 50; my $one = 'The $cash variable is $' . $cash; my $two = "The \$cash variable is \$$cash"; print $one . "\n"; print "$two \n";

6. Trick #3:use strict $str = "Hello, World\n"; print "The value in str is $Str"; • BAD! • use strict; • my $str = "Hello, World\n"; • print "The value in str is $Str"; • - GOOD!

7. Trick #4:Become a scope master use strict; { my $name = "joe"; } print $name;

8. Trick #5: File Handles my $f = open_file("TRICK1.TXT"); while (<$f>) { print $_; } sub open_file { my $file = shift; open INFILE, $file || die "Could not open $f for read"; return(\*INFILE); }

9. Trick #6: use croak use Carp; my $f = open_file("TRICK2.TXT"); while (<$f>) { print $_; } sub open_file { my $file = shift; open INFILE, $file or croak "Could not open $file for read"; return(\*INFILE); }

10. Trick #7: Handle Exceptions with eval use Carp; eval(run()); if ($@) { print "Died with message $@\n"; } sub run { croak "ribbet. ribbet.\n"; }

11. Trick #8:Use Warnings use warnings; my $val; $val = $val+5; # or ($val = val + 5); print "val is $val\n";

12. Trick #9To create an error log, re-direct STDERR trick8.pl 2>err.txt

13. Trick #10:ArrayRefs as output my $rasquares = get_squares(16); print "The square of 8 is $rasquares->[8]\n"; sub get_squares { my $num = shift; my @arr; if ($num<1) { croak "get_squares must be a number"; } for (my $idx=0; $idx<$num; $idx++) { $arr[$idx]=$idx*$idx; } return \@arr; }

14. Trick #11:Avoid C-Style for loops … use foreach my $rasquares = get_squares(16); my $idx; foreach my $val (@$rasquares) { print "$val\n"; } sub get_squares { my $num = shift; my @arr; if ($num<1) { croak "get_squares must be a number"; } for (my $idx=0; $idx<$num; $idx++) { $arr[$idx]=$idx*$idx; } return \@arr; }

15. Trick #12:Use ‘Named Parameters’ my %params = ('height',10,'length',5,'width',3); print volume(%params); sub volume { my %param = @_; return $param{'height'}*$param{'width'}*$param{'length'}; }

16. Trick #13:Direct-Attack your RegExps sub convert { my $num = shift; $num=~s/^616-5/269-5/g; $num=~s/^616-31/269-31/g; $num=~s/^616-32/269-32/g; return $num; }

17. Trick #14:Use Regular Expression Memory my %switches; open INFILE, "trick12.txt" or croak "failed to open trick12.txt for read"; while(my $str = <INFILE>) { $str=~ /^\d\d\d-(\d\d\d)-\d\d\d\d/; my $switch = $1; if (!defined($switches{$switch})) { $switches{$switch} = 0; } $switches{$switch}++; print "$switch\n"; }

18. Trick #15:Create lists of lists with references my $tictac; my ($idx, $jdx); for ($idx=0; $idx<3; $idx++) { for ($jdx=0; $jdx<3;$jdx++) { $tictac->[$idx]->[$jdx] = "-"; } }

19. Trick #16:Read a file into an array chomp(my @data = <INFILE>);

20. Trick #17:Turn off Warnings when you want use warnings; my @arr; $arr[0] = 'Some'; $arr[1] = 'Values'; $arr[3] = 'And some whitespace'; $arr[5] = 'To be Concatenated'; my $str = join(',', @arr); print $str . "\n"; { no warnings; my $str = join(',', @arr); print $str . "\n"; }

21. Trick #18:use backticks my $str = `ls -l`; my @arr = split(/\n/, $str); my $file = $arr[0]; $file=~/[-rwxa][-rwxa][-rwxa][-rwxa]\s*(\d*)\s/; my $size = $1; $file=~/\s200\d\s\s([\w\W]*)/; my $name = $1; print "$name has a size of $size";

22. Trick #19:‘Sniff’ files with –e and -s • Or –x, -o, -d, -T,-B, -M … if (-e 'trick19.pl') { my $size = -s 'trick19.pl'; print "The size of trick19.pl is $size \n"; }

23. Trick #20:Avoid manipulating @_ … … Unless you really want to. my $total = 6; double($total); print "Total is $total\n"; sub double { $_[0]*=2; }

24. Trick #21:Named parameters via anonymous hashrefs print volume({height=>10, length=>5, width=>3}); sub volume { my $rparam = shift; return $rparam->{'height'} *$rparam->{'width'} *$rparam->{'length'}; }

25. Trick #22:Make your subs type-safe sub volume { my $rparam = shift; if (!defined($rparam) || ref($rparam) ne 'HASH') { croak('volume function expects a hashref'); } return $rparam->{'height'} *$rparam->{'width'} *$rparam->{'length'}; }

26. Trick #23 - Decode • $foo = $str ? 'Y' : 'N';

27. Trick #24Pull off parameters • $isTest = $parameters =~ s/^(TEST)//;

28. Trick #26Use map @doubled = map { $_*=2} @single; # Doubles the numerical #value of a list

29. Trick #27Use grep $matches = grep /\$/, @costs; @us_dollars = grep /\$/, @costs;

30. Trick #28Learn to use pop, push, shift, unshift # AN ARRAY @coins = ("Quarter", "Dime", "Nickel"); # ADD ELEMENTS push(@coins, "Penny"); print "@coins""; unshift(@coins, "Dollar"); print "@coins"; # REMOVE ELEMENTS pop(@coins); print "@coins"; shift(@coins);

31. Trick #28:Use CPAN / PPM • www.cpan.org • Under win32, PPM

32. Trick #29:Use a tight-feedback-loop environment • putty / vim

33. What to do tomorrow • Go to xndev.com • Get this powerpoint • Print it … read it … apply it

34. What to do next week • Buy a book • Experiment with new techniques

35. What to do next year • Give a lightning talk • Speak at PM’s? • Attend a conference • YAPC::NA is cheap

36. Bonus: What are your favs? • Discuss the favorite tips & techniques of the audience.