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
$_
To quit from the shell, hit "Ctrl+D" or "Ctrl+C".
MSWin32 NOTE: control keys won't work if TERM=dumb
because readline functionality will be disabled.
RunControlFiles
For particular projects you might well end up running the same commands each time the REPL shell starts
up - loading Perl modules, setting configuration, and so on. A run control file lets you have this done
automatically, and you can have multiple files for different projects.
By default the "re.pl" program looks for "$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 forward slash, 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 "Standard" profile ships with "Devel::REPL"; it loads the following plugins (note that some of these
require optional features -- or you can also use the "Minimal" profile):
• 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
• Devel::REPL::Plugin::Colors
• Devel::REPL::Plugin::Completion
• Devel::REPL::Plugin::CompletionDriver::INC
• Devel::REPL::Plugin::CompletionDriver::LexEnv
• Devel::REPL::Plugin::CompletionDriver::Keywords
• Devel::REPL::Plugin::CompletionDriver::Methods
• Devel::REPL::Plugin::ReadlineHistory
Plugins
Plugins are a way to add functionality 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. These plugins can be loaded in your
$HOME/.re.pl/repl.rc like:
load_plugin qw( CompletionDriver::Global DumpHistory );
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".
TheREPLshellobject
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
$_
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