1Devel::REPL::Overview(3U)ser Contributed Perl DocumentatiDoenvel::REPL::Overview(3)
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NAME

6       Devel::REPL::Overview - overview of Devel::REPL.
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DESCRIPTION

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
14       • Quickly test some thought or tricky expression
15
16       • Run some code bigger than one line without a temporary file
17
18       • Play around with libraries and modules
19
20       • You can even call a console in your script and play around in
21         script's context
22
23       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
29   Devel::REPL - the Perl console
30       REPL stands for Read, Evaluate, Print, Loop.  Lets install and try it.
31
32              $ cpan Devel::REPL
33
34       After installation you have a lot of new modules, but the most
35       interesting things are:
36
37       • Devel::REPL
38           A top level module.
39
40       • re.pl
41           Wrapper script, running console.
42
43       And a bunch of plugins (I'll describe them later).  In command line
44       type:
45
46             $ re.pl
47
48       If everything is ok you'll see a prompt (underlined $).  That's it. You
49       can start typing expressions.
50
51       An example session:
52
53         $ sub factorial {
54
55         > my $number = shift;
56
57         > return $number > 1 ? $number * factorial($number-1) : $number;
58
59         > }
60
61         $ factorial 1 # by the way, comments are allowed
62
63         1 # our return value
64
65         $ factorial 5
66
67         120
68
69         $ [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
80         $ {apple=>1,fruit=>'apple',cart=>['apple','banana']}
81         $HASH1 = {
82                   apple => 1,
83                   cart  => [
84                             'apple',
85                             'banana'
86                   ],
87                   fruit => 'apple'
88         };
89
90         $ package MyPackage; # create a package
91
92         $ sub say_hi { # define a sub
93
94         > print "Hi!\n";
95
96         > } # statement is evaluated only after we've finished typing block.
97             # See Plugins section.
98         > __PACKAGE__
99         MyPackage
100         > package main;
101
102         > __PACKAGE_
103         main
104         > MyPackage->say_hi
105         Hi!
106         1
107         $
108
109   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
114       The default control file is located at $HOME/.re.pl/repl.rc.
115
116       You can store there any statements you would normally type in.
117
118       I.e. my $HOME/.re.pl/repl.rc has next lines:
119
120             use feature 'say'; # to don't write \n all the time
121
122             use Data::Dumper;
123
124             # pretty print data structures
125             sub pp { print Data::Dumper->Dump([@_]) }
126
127       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
131             $ re.pl --rcfile /path/to/your/rc.file
132
133       If your rc-file is in $HOME/.re.pl directory, you can omit the path:
134
135             $ re.pl --rcfile rc.file
136
137       If you have rc-file with the same name in current directory and you
138       don't want to type path, you can:
139
140             $ re.pl --rcfile ./rc.file
141
142   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
146       • Devel::REPL::Plugin::History
147           No comments. Simply history.
148
149       • Devel::REPL::Plugin::!LexEnv
150           Provides a lexical environment for the Devel::REPL.
151
152       • Devel::REPL::Plugin::DDS
153           Formats return values with Data::Dump::Streamer module.
154
155       • Devel::REPL::Plugin::Packages
156           Keeps track of which package your're in.
157
158       • Devel::REPL::Plugin::Commands
159           Generic command creation plugin using injected functions.
160
161       • 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
166                $ sub mysub {
167
168                > print "Hello, World!\n"; ## notice prompt change
169
170                > }
171
172                $ mysub
173                Hello, World!
174                1
175                $
176
177           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
180       There are lots of contributed plugins you can find at CPAN.
181

Profiles

183       If plugins change and extend functionality of Devel::REPL, profiles are
184       changing your environment (loaded plugins, constants, subs and etc.).
185
186       For example, the Minimal profile, Devel::REPL::Profile::Minimal:
187
188             package Devel::REPL::Profile::Minimal;
189
190             use Moose; ### advanced OOP system for Perl
191
192             ### keep those exports/imports out of our namespace
193             use namespace::autoclean;
194
195             with 'Devel::REPL::Profile';  ## seem perldoc Muse
196
197             sub plugins { ### plugins we want to be loaded
198               qw(History LexEnv DDS Packages Commands MultiLine::PPI);
199             }
200
201             ### 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
207               $repl->load_plugin($_) for $self->plugins; ### load our plugins
208             }
209
210             1;
211
212       There is also the StandardDevel::REPL::Profile::Standard profile, which
213       contains a number of optional (yet very useful) features.
214
215       To enable some profile use the "--profile" switch:
216
217             $ re.pl --profile SomeProfile
218
219       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).
222

SEE ALSO

224perl v5.36.0                      2022-07-22          Devel::REPL::Overview(3)
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