diff options
| -rw-r--r-- | perl.html.markdown | 85 |
1 files changed, 45 insertions, 40 deletions
diff --git a/perl.html.markdown b/perl.html.markdown index 61e8cd0e..3cbd2801 100644 --- a/perl.html.markdown +++ b/perl.html.markdown @@ -21,9 +21,9 @@ use strict; use warnings; # All perl scripts and modules should include these lines. Strict causes -# compilation to fail in cases like misspelled variable names, and warnings -# will print warning messages in case of common pitfalls like concatenating -# to an undefined value. +# compilation to fail in cases like misspelled variable names, and +# warnings will print warning messages in case of common pitfalls like +# concatenating to an undefined value. #### Perl variable types @@ -47,8 +47,8 @@ my @animals = ("camel", "llama", "owl"); my @numbers = (23, 42, 69); my @mixed = ("camel", 42, 1.23); -# Array elements are accessed using square brackets, with a $ to indicate -# one value will be returned. +# Array elements are accessed using square brackets, with a $ to +# indicate one value will be returned. my $second = $animals[1]; ## Hashes @@ -56,7 +56,8 @@ my $second = $animals[1]; my %fruit_color = ("apple", "red", "banana", "yellow"); -# You can use whitespace and the "=>" operator to lay them out more nicely: +# You can use whitespace and the "=>" operator to lay them out more +# nicely: my %fruit_color = ( apple => "red", @@ -71,8 +72,8 @@ my $color = $fruit_color{apple}; #### References -# More complex data types can be constructed using references, which allow -# you to build arrays and hashes within arrays and hashes. +# More complex data types can be constructed using references, which +# allow you to build arrays and hashes within arrays and hashes. my $array_ref = \@array; my $hash_ref = \%hash; @@ -88,13 +89,14 @@ my $colors = {apple => "red", banana => "yellow"}; my @fruits_array = @$fruits; my %colors_hash = %$colors; -# As a shortcut, the arrow operator can be used to dereference and access a -# single value. +# As a shortcut, the arrow operator can be used to dereference and +# access a single value. my $first = $array_ref->[0]; my $value = $hash_ref->{banana}; -# See perlreftut and perlref for more in-depth documentation on references. +# See perlreftut and perlref for more in-depth documentation on +# references. #### Conditional and looping constructs @@ -150,18 +152,18 @@ print $hash_ref->{$_} for keys %$hash_ref; #### 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: +# 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 $a contains "foo" +if ($x =~ /foo/) { ... } # true if $x contains "foo" # Simple substitution -$a =~ s/foo/bar/; # replaces foo with bar in $a -$a =~ s/foo/bar/g; # replaces ALL INSTANCES of foo with bar in $a +$x =~ s/foo/bar/; # replaces foo with bar in $x +$x =~ s/foo/bar/g; # replaces ALL INSTANCES of foo with bar in $x #### Files and I/O @@ -172,9 +174,10 @@ open(my $in, "<", "input.txt") or die "Can't open input.txt: $!"; open(my $out, ">", "output.txt") or die "Can't open output.txt: $!"; open(my $log, ">>", "my.log") or die "Can't open my.log: $!"; -# You can read from an open filehandle using the "<>" operator. In scalar -# context it reads a single line from the filehandle, and in list context it -# reads the whole file in, assigning each line to an element of the list: +# You can read from an open filehandle using the "<>" operator. In +# scalar context it reads a single line from the filehandle, and in list +# context it reads the whole file in, assigning each line to an element +# of the list: my $line = <$in>; my @lines = <$in>; @@ -197,9 +200,9 @@ logger("We have a logger subroutine!"); #### Modules -# A module is a set of Perl code, usually subroutines, which can be used in -# other Perl code. It is usually stored in a file with the extension .pm so -# that Perl can find it. +# A module is a set of Perl code, usually subroutines, which can be used +# in other Perl code. It is usually stored in a file with the extension +# .pm so that Perl can find it. package MyModule; use strict; @@ -219,24 +222,25 @@ sub trim { use MyModule; MyModule::trim($string); -# The Exporter module can help with making subroutines exportable, so they -# can be used like this: +# The Exporter module can help with making subroutines exportable, so +# they can be used like this: use MyModule 'trim'; trim($string); -# Many Perl modules can be downloaded from CPAN (http://www.cpan.org/) and -# provide a range of features to help you avoid reinventing the wheel. A -# number of popular modules like Exporter are included with the Perl -# distribution itself. See perlmod for more details on modules in Perl. +# Many Perl modules can be downloaded from CPAN (http://www.cpan.org/) +# and provide a range of features to help you avoid reinventing the +# wheel. A number of popular modules like Exporter are included with +# the Perl distribution itself. See perlmod for more details on modules +# in Perl. #### Objects -# Objects in Perl are just references that know which class (package) they -# belong to, so that methods (subroutines) called on it can be found there. -# The bless function is used in constructors (usually new) to set this up. -# However, you never need to call it yourself if you use a module like Moose -# or Moo (see below). +# Objects in Perl are just references that know which class (package) +# they belong to, so that methods (subroutines) called on it can be +# found there. The bless function is used in constructors (usually new) +# to set this up. However, you never need to call it yourself if you use +# a module like Moose or Moo (see below). package MyCounter; use strict; @@ -260,7 +264,8 @@ sub increment { 1; -# Methods can be called on a class or object instance with the arrow operator. +# Methods can be called on a class or object instance with the arrow +# operator. use MyCounter; my $counter = MyCounter->new; @@ -268,9 +273,9 @@ print $counter->count, "\n"; # 0 $counter->increment; print $counter->count, "\n"; # 1 -# The modules Moose and Moo from CPAN can help you set up your object classes. -# They provide a constructor and simple syntax for declaring attributes. This -# class can be used equivalently to the one above. +# The modules Moose and Moo from CPAN can help you set up your object +# classes. They provide a constructor and simple syntax for declaring +# attributes. This class can be used equivalently to the one above. package MyCounter; use Moo; # imports strict and warnings @@ -284,8 +289,8 @@ sub increment { 1; -# Object-oriented programming is covered more thoroughly in perlootut, and its -# low-level implementation in Perl is covered in perlobj. +# Object-oriented programming is covered more thoroughly in perlootut, +# and its low-level implementation in Perl is covered in perlobj. ``` #### FAQ |