NAME
Devel::REPL - a modern perl interactive shell
SYNOPSIS
my $repl = Devel::REPL->new;
$repl->load_plugin($_) for qw(History LexEnv);
$repl->run
Alternatively, use the 're.pl' script installed with the distribution
system$ re.pl
DESCRIPTION
This is an interactive shell for Perl, commonly known as a REPL - Read,
Evaluate, Print, Loop. The shell provides for rapid development or
testing of code without the need to create a temporary source code file.
Through a plugin system, many features are available on demand. You can
also tailor the environment through the use of profiles and run control
files, for example to pre-load certain Perl modules when working on a
particular project.
USAGE
To start a shell, follow one of the examples in the "SYNOPSIS" above.
Once running, the shell accepts and will attempt to execute any code
given. If the code executes successfully you'll be shown the result,
otherwise an error message will be returned. Here are a few examples:
$_ print "Hello, world!\n"
Hello, world!
1
$_ nosuchfunction
Compile error: Bareword "nosuchfunction" not allowed while "strict subs" in use at (eval 130) line 5.
$_
In the first example above you see the output of the command ("Hello,
world!"), if any, and then the return value of the statement (1).
Following that example, an error is returned when the execution of some
code fails.
Note that the lack of semicolon on the end is not a mistake - the code
is run inside a Block structure (to protect the REPL in case the code
blows up), which means a single statement doesn't require the semicolon.
You can add one if you like, though.
If you followed the first example in the "SYNOPSIS" above, you'll have
the History and LexEnv plugins loaded (and there are many more
available). Although the shell might support "up-arrow" history, the
History plugin adds "bang" history to that so you can re-execute chosen
commands (with e.g. "!53"). The LexEnv plugin ensures that lexical
variables declared with the "my" keyword will automatically persist
between statements executed in the REPL shell.
When you "use" any Perl module, the "import()" will work as expected -
the exported functions from that module are available for immediate use:
$_ carp "I'm dieeeing!\n"
String found where operator expected at (eval 129) line 5, near "carp "I'm dieeeing!\n""
(Do you need to predeclare carp?)
Compile error: syntax error at (eval 129) line 5, near "carp "I'm dieeeing!\n""
BEGIN not safe after errors--compilation aborted at (eval 129) line 5.
$_ use Carp
$_ carp "I'm dieeeing!\n"
I'm dieeeing!
at /usr/share/perl5/Lexical/Persistence.pm line 327
1
$_
To quit from the shell, hit "control+d" or "control+c".
Run Control Files
For particular projects you might well end up running the same commands
each time the REPL shell starts up - loading Perl modules, setting
configuration, and so on. A run control file lets you have this done
automatically, and you can have multiple files for different projects.
By default the "re.pl" program looks for "$HOME/.re.pl/repl.rc", and
runs whatever code is in there as if you had entered it at the REPL
shell yourself.
To set a new run control file that's also in that directory, pass it as
a filename like so:
system$ re.pl --rcfile myproject.pc
If the filename happens to contain a forwardslash, then it's used
absolutely, or realive to the current working directory:
system$ re.pl --rcfile /path/to/my/project/repl.rc
Within the run control file you might want to load plugins. This is
covered in "The REPL shell object" section, below.
Profiles
To allow for the sharing of run control files, you can fashion them into
a Perl module for distribution (perhaps via the CPAN). For more
information on this feature, please see the Devel::REPL::Profile manual
page.
A default profile ships with "Devel::REPL"; it loads the following
plugins:
* Devel::REPL::Plugin::History
* Devel::REPL::Plugin::LexEnv
* Devel::REPL::Plugin::DDS
* Devel::REPL::Plugin::Packages
* Devel::REPL::Plugin::Commands
* Devel::REPL::Plugin::MultiLine::PPI
Plugins
Plugins are a way to add funcionality to the REPL shell, and take
advantage of "Devel::REPL" being based on the Moose object system for
Perl 5. This means it's simple to 'hook into' many steps of the R-E-P-L
process. Plugins can change the way commands are interpreted, or the way
their results are output, or even add commands to the shell environment.
A number of plugins ship with "Devel::REPL", and more are available on
the CPAN. Some of the shipped plugins are loaded in the default profile,
mentioned above.
Writing your own plugins is not difficult, and is discussed in the
Devel::REPL::Plugin manual page, along with links to the manual pages of
all the plugins shipped with "Devel::REPL".
The REPL shell object
From time to time you'll want to interact with or manipulate the
"Devel::REPL" shell object itself; that is, the instance of the shell
you're currently running.
The object is always available through the $_REPL variable. One common
requirement is to load an additional plugin, after your profile and run
control files have already been executed:
$_ $_REPL->load_plugin('Timing');
1
$_ print "Hello again, world!\n"
Hello again, world!
Took 0.00148296356201172 seconds.
1
$_
REQUIREMENTS
In addition to the contents of the standard Perl distribution, you will
need the following:
* Moose >= 0.64
* MooseX::Object::Pluggable >= 0.0009
* MooseX::Getopt >= 0.15
* MooseX::AttributeHelpers >= 0.14
* namespace::clean
* File::HomeDir
* Task::Weaken
Optionally, some plugins if installed will require the following
modules:
* PPI
* Data::Dump::Streamer
* File::Next
* B::Keywords
* Lexical::Persistence
* App::Nopaste
* Module::Refresh
AUTHOR
Matt S Trout - mst (at) shadowcatsystems.co.uk
(<http://www.shadowcatsystems.co.uk/>)
CONTRIBUTORS
Stevan Little - stevan (at) iinteractive.com
Alexis Sukrieh - sukria+perl (at) sukria.net
epitaph
mgrimes - mgrimes (at) cpan dot org
Shawn M Moore - sartak (at) gmail.com
Oliver Gorwits - oliver on irc.perl.org
LICENSE
This library is free software under the same terms as perl itself