1Devel::REPL::Overview(3U)ser Contributed Perl DocumentatiDoenvel::REPL::Overview(3)
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6 Devel::REPL::Overview - overview of Devel::REPL.
7
9 What is a console? How it can assist you?
10 Most modern languages have consoles. The console is an interactive tool
11 that evaluates your input while you type it. It gives you several
12 advantages:
13 • Quickly test some thought or tricky expression
15 • Run some code bigger than one line without a temporary file
17 • Play around with libraries and modules
19 • You can even call a console in your script and play around in
21 script's context
22 For Ruby it would be irb, for Python is... python by itself and for
24 perl... and there was nothing for perl (except that ugly perl -d -e ""
25 and several failed projects) until Devel::REPL was written by Matt S
26 Trout (a.k.a. mst) from ShadowCatSystems
27 <http://www.shadowcatsystems.co.uk>.
28 Devel::REPL - the Perl console
30 REPL stands for Read, Evaluate, Print, Loop. Lets install and try it.
31 $ cpan Devel::REPL
33 After installation you have a lot of new modules, but the most
35 interesting things are:
36 • Devel::REPL
38 A top level module.
39 • re.pl
41 Wrapper script, running console.
42 And a bunch of plugins (I'll describe them later). In command line
44 type:
45 $ re.pl
47 If everything is ok you'll see a prompt (underlined $). That's it. You
49 can start typing expressions.
50 An example session:
52 $ sub factorial {
54 > my $number = shift;
56 > return $number > 1 ? $number * factorial($number-1) : $number;
58 > }
60 $ factorial 1 # by the way, comments are allowed
62 1 # our return value
64 $ factorial 5
66 120
68 $ [1,2,3,4,5,6,7]
70 $ARRAY1 = [
71 1,
72 2,
73 3, # return values are printed with Data::Dumper::Streamer.
74 4, # See Plugins section
75 5,
76 6,
77 7
78 ];
79 $ {apple=>1,fruit=>'apple',cart=>['apple','banana']}
81 $HASH1 = {
82 apple => 1,
83 cart => [
84 'apple',
85 'banana'
86 ],
87 fruit => 'apple'
88 };
89 $ package MyPackage; # create a package
91 $ sub say_hi { # define a sub
93 > print "Hi!\n";
95 > } # statement is evaluated only after we've finished typing block.
97 # See Plugins section.
98 > __PACKAGE__
99 MyPackage
100 > package main;
101 > __PACKAGE_
103 main
104 > MyPackage->say_hi
105 Hi!
106 1
107 $
108 Control files a.k.a. I don't want to type it every time
110 Devel::REPL has a control files feature. Control files are evaluated on
111 session start in the same way as you would type them manually in the
112 console.
113 The default control file is located at $HOME/.re.pl/repl.rc.
115 You can store there any statements you would normally type in.
117 I.e. my $HOME/.re.pl/repl.rc has next lines:
119 use feature 'say'; # to don't write \n all the time
121 use Data::Dumper;
123 # pretty print data structures
125 sub pp { print Data::Dumper->Dump([@_]) }
126 You can have multiple control files and they can be anywhere in the
128 file system. To make re.pl use some rc-file other than repl.rc, call it
129 like this:
130 $ re.pl --rcfile /path/to/your/rc.file
132 If your rc-file is in $HOME/.re.pl directory, you can omit the path:
134 $ re.pl --rcfile rc.file
136 If you have rc-file with the same name in current directory and you
138 don't want to type path, you can:
139 $ re.pl --rcfile ./rc.file
141 I want it to bark, fly, jump and swim! or Plugins
143 Plugins extend functionality and change behavior of Devel::REPL.
144 Bundled plugins are:
145 • Devel::REPL::Plugin::History
147 No comments. Simply history.
148 • Devel::REPL::Plugin::!LexEnv
150 Provides a lexical environment for the Devel::REPL.
151 • Devel::REPL::Plugin::DDS
153 Formats return values with Data::Dump::Streamer module.
154 • Devel::REPL::Plugin::Packages
156 Keeps track of which package your're in.
157 • Devel::REPL::Plugin::Commands
159 Generic command creation plugin using injected functions.
160 • Devel::REPL::Plugin::MultiLine::PPI
162 Makes Devel::REPL read your input until your block
163 is finished. What does this means: you can type a part of a block
164 on one line and second part on another:
165 $ sub mysub {
167 > print "Hello, World!\n"; ## notice prompt change
169 > }
171 $ mysub
173 Hello, World!
174 1
175 $
176 but this *doesn't* mean you can print sub name or identifier
178 on several lines. Don't do that! It won't work.
179 There are lots of contributed plugins you can find at CPAN.
181
183 If plugins change and extend functionality of Devel::REPL, profiles are
184 changing your environment (loaded plugins, constants, subs and etc.).
185 For example, the Minimal profile, Devel::REPL::Profile::Minimal:
187 package Devel::REPL::Profile::Minimal;
189 use Moose; ### advanced OOP system for Perl
191 ### keep those exports/imports out of our namespace
193 use namespace::autoclean;
194 with 'Devel::REPL::Profile'; ## seem perldoc Muse
196 sub plugins { ### plugins we want to be loaded
198 qw(History LexEnv DDS Packages Commands MultiLine::PPI);
199 }
200 ### the only required sub for profile,
202 ### it is called on profile activation
203 sub apply_profile {
204 my ($self, $repl) = @_;
205 ### $self - no comments, $repl - current instance of Devel::REPL
206 $repl->load_plugin($_) for $self->plugins; ### load our plugins
208 }
209 1;
211 There is also the StandardDevel::REPL::Profile::Standard profile, which
213 contains a number of optional (yet very useful) features.
214 To enable some profile use the "--profile" switch:
216 $ re.pl --profile SomeProfile
218 Alternatively, you can set the environment variable
220 "DEVEL_REPL_PROFILE" to "SomeProfile", or set the "profile" key in your
221 "rcfile" (see Devel::REPL for more information).
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224perl v5.34.0 2021-07-22 Devel::REPL::Overview(3)