Provided by: libregexp-debugger-perl_0.002007-1_all 
NAME
Regexp::Debugger - Visually debug regexes in-place
VERSION
This document describes Regexp::Debugger version 0.002007
SYNOPSIS
use Regexp::Debugger;
DESCRIPTION
When you load this module, any regex in the same lexical scope will be visually (and interactively)
debugged as it matches.
INTERFACE
The module itself provides no API. You load it and the debugger is automatically activated in that
lexical scope.
The debugger offers the following commands:
"?" : Print a help message listing these commands
"s" : Step forward (stepping into any named subpattern calls)
"n" : Step forward (stepping over any named subpattern calls)
"-" : Step backward (stepping into any named subpattern calls)
"p" : Step backward (stepping over any named subpattern calls)
"r" : Continue forward until the end of the current (sub)pattern
"m" : Continue forward to the next regex component that matches
"M" : Continue forward to the next regex component that matches
in the current (sub)pattern (i.e. silently stepping over
any named subpattern calls)
"f" : Continue forward to the next regex component that fails
to match something
"F" : Continue forward to the next regex component that fails
to match something in the current (sub)pattern
(i.e. silently stepping over any named subpattern calls)
"c" : Continue forward until the entire regex matches
or completely backtracks
"C" : Continue forward until the entire regex matches
or completely backtracks, silently stepping over
any named subroutine calls
"R" : Rewind to the start of the entire match
"<RETURN>/<ENTER>"
: Repeat the previous command
"v" : Switch to regex/string visualization mode
"h" : Switch to heatmapped visualization mode
"e" : Switch to the event log
"j" : Switch to the underlying JSON data
"d" : Describe each component of the regex in detail
"V"
"H"
"E"
"J"
"D" : Take a snapshot of the corresponding display mode.
When prompted for a filename:
"<RET>"
...prints the snapshot to the terminal
"<TAB>"
...prints the snapshot to a file named "./rxrx_DISPLAY_MODE_TIMESTAMP"
Anything else
...prints the snapshot to that file
"q" : Quit the debugger and finish matching this regex
without any further visualization. The program
continues to execute and other regexes may
still be debugged.
"x" : Exit the debugger and the entire program immediately.
CONFIGURATION
You can configure the debugger by setting up a .rxrx file in in the current directory or in your home
directory. This configuration consists of single-line key:value pairs (everything else in the file is
silently ignored).
Display mode configuration
If the "'display'" key is specified, the debugger starts in that mode. The four available modes are:
# Show dynamic visualization of matching (the default)...
display : visual
# Show dynamic heatmap visualization of matching...
display : heatmap
# Show multi-line matching event log...
display : events
# Show JSON encoding of matching process...
display : JSON
Whitespace display configuration
Normally, the debugger compacts whitespaces in the regex down to a single space character, but you can
configure that with the "show_ws" key:
# Compact whitespace and comments to a single space (the default)...
show_ws : compact
# Compact whitespace, but show comments, newlines (\n), and tabs (\t)...
show_ws : visible
# Don't compact whitespace, and show newlines and tabs as \n and \t...
show_ws : original
Colour configuration
The following keys reconfigure the colours with which the debugger displays various information:
Colours for debugging information
• "try_col"
The colour in which attempts to match part of the regex are reported
• "match_col"
The colour in which successful matches of part of the regex are reported
• "fail_col"
The colour in which unsuccessful matches of part of the regex are reported
• "ws_col"
The colour in which special characters (such as "\n", "\t", "\e", etc.) are reported (as single
letters: 'n', 't', 'e', etc.)
• "info_col"
The colour in which other information is reported
Colours for regex descriptions
• "desc_regex_col"
The colour in which components of the regex are displayed
• "desc_text_col"
The colour in which descriptions of regex components are displayed
• "desc_sep_col"
The colour in which separators between component descriptions are displayed.
Colours for heatmaps
Any key that starts with "heatmap"... is treated as a specifier for an equal part of the total range of
each heatmap.
These names are sorted (numerically, if possible; otherwise alphabetically) and the corresponding values
are then used to display equal percentiles from the heatmap.
For example (using numeric sorting):
heatmap_0_colour : cyan on_black # 0-33rd percentile
heatmap_50_colour : yellow on_black # 34-66th percentile
heatmap_100_colour : red on_black # 67-100th percentile
Or, equivalently (using alphabetic sorting):
heatmap_infrequent : cyan on_black # 0-33rd percentile
heatmap_more_frequent : yellow on_black # 34-66th percentile
heatmap_very_frequent : red on_black # 67-100th percentile
Colour specifications
The colour values that may be used in any of the above colour specifications are any combination of the
following (i.e. the colour specifiers supported by the Term::ANSIColor module):
clear reset bold dark
faint underline underscore blink
reverse concealed
black red green yellow
blue magenta cyan white
bright_black bright_red bright_green bright_yellow
bright_blue bright_magenta bright_cyan bright_white
on_black on_red on_green on_yellow
on_blue on_magenta on_cyan on_white
on_bright_black on_bright_red on_bright_green on_bright_yellow
on_bright_blue on_bright_magenta on_bright_cyan on_bright_white
The default colour configurations are:
try_col : bold magenta on_black
match_col : bold cyan on_black
fail_col : yellow on_red
ws_col : bold blue underline
info_col : white on_black
desc_regex_col : white on_black
desc_text_col : cyan on_black
desc_sep_col : blue on_black underline
heatmap__20th_percentile : white on_black
heatmap__40th_percentile : cyan on_blue
heatmap__60th_percentile : blue on_cyan
heatmap__80th_percentile : red on_yellow
heatmap_100th_percentile : yellow on_red
Output configuration
Normally Regexp::Debugger sends its visualizations to the terminal and expects input from the same
device.
However, you can configure the module to output its information (in standard JSON format) to a nominated
file instead, using the 'save_to' option:
save_to : filename_to_save_data_to.json
Data saved in this way may be re-animated using the "rxrx" utility, or by calling
"Regexp::Debugger::rxrx()" directly. (See: "COMMAND-LINE DEBUGGING" for details).
Configuration API
You can also configure the debugger on a program-by-program basis, by passing any of the above key/value
pairs when the module is loaded.
For example:
use Regexp::Debugger fail => 'bold red', whitespace => 'compact';
Note that any configuration specified in the user's .rxrx file is overridden by an explicit specification
of this type.
The commonest use of this mechanism is to dump regex debugging information from an non-interactive
program:
use Regexp::Debugger save_to => 'regex_debugged.json';
Note that, when 'save_to' is specified within a program, the value supplied does not have to be a string
specifying the filename. You can also provide an actual filehandle (or equivalent). For example:
use Regexp::Debugger save_to => IO::Socket::INET->new(
Proto => "tcp",
PeerAddr => 'localhost:666',
);
COMMAND-LINE DEBUGGING
The module provides a non-exported subroutine ("rxrx()") that implements a useful command-line regex
debugging utility.
The utility can be invoked with:
perl -MRegexp::Debugger -E 'Regexp::Debugger::rxrx\(@ARGV\)'
which is usually aliased in the shell to "rxrx" (and will be referred to by that name hereafter).
Regex debugging REPL
When called without any arguments, "rxrx" initiates a simple REPL that allows the user to type in regexes
and strings and debug matches between them:
• Any line starting with a "/" is treated as a new regex to match with. The closing "/" may be
omitted. If the closing "/" is supplied, any one or more of the following flags may be specified
immediately after it: "x", "i", "m", "s", "a", "u", "d", "l".
• Any line starting with a "+/" is treated as the first line of a new multi- line regex to match with.
Subsequent lines are added to the regex until the closing "/" is encountered. Any one or more of the
following flags may be specified immediately after the closing "/": "x", "i", "m", "s", "a", "u",
"d", "l".
• Any line starting with a "'" or """ is treated as a new string to match against. The corresponding
closing delimiter may be omitted.
• Any line beginning with "m" causes the REPL to match the current regex against the current string,
visualizing the match in the usual way.
• Any line beginning with "g" causes the REPL to exhaustively match the current regex against the
current string (i.e. as if the regex had a /g flag), visualizing all the matches in the usual way.
• Any line beginning with "d" causes the REPL to display a detailed decomposition and explanation of
the current regex.
• Any line beginning with "q" or "x" causes the REPL to quit and exit.
• Any line beginning with "?" invokes the help listing for the REPL.
If the IO::Prompter module (version 0.004 or later) is available, the input process remembers its
history, which you can recall by typing "CTRL-R". Repeated "CTRL-R"'s step successively backwards through
earlier inputs. "CTRL-N" steps successfully forward again. You can then use
"CTRL-B"/"CTRL-F"/"CTRL-A"/"CTRL-E" to move the cursor around the line of recalled input, to delete or
insert characters. This is useful for modifying and retrying a recently entered regex or string.
Debugging regexes from a dumped session
When called with a filename, "rxrx" first checks whether the file contains a JSON dump of a previous
debugging, in which case it replays the visualization of that regex match interactively.
This is useful for debugging non-interactive programs where the 'save_to' option was used (see "Output
configuration" and "Configuration API").
In this mode, all the features of the interactive debugger (as listed under "INTERFACE") are fully
available: you can step forwards and backwards through the match, skip to the successful submatch or a
breakpoint, swap visualization modes, and take snapshots.
Wrap-around regex debugging
When called with the name of a file that does not contain a JSON dump, "rxrx" attempts to execute the
file as a Perl program, with Regexp::Debugger enabled at the top level. In other words:
rxrx prog.pl
is a convenient shorthand for:
perl -MRegexp::Debugger prog.pl
LIMITATIONS
"/x"-mode comments
Due to limitations in the Perl "overload::constant()" mechanism, the current implementation cannot always
distinguish whether a regex has an external /x modifier (and hence, what whitespace and comment
characters mean). Whitespace is handled correctly in almost all cases, but comments are sometimes not.
When processing a "# comment to end of line" within a regex, the module currently assumes a "/x" is in
effect at start of the regex (unless that assumption causes the regex to fail to compile). This will
sometimes cause erroneous behaviour if an unescaped "#" is used in a non-"/x" regex.
Unfortunately, this limitation is unlikely to be fully removed in a future release, unless an additional
flag-detection mechanism is added to "overload::constant()".
Note, however, that this limitation does not affect the handling of comments in "(?x:...)" blocks or of
literal "#" in "(?-x:...)" blocks within a regex. These are always correctly handled, which means that
explicitly using either of these blocks is a reliable workaround. Alternatively, there is no problem if
you always use the "/x" modifier on every debugged regex (for example, via "use re '/x'"). Nor if you
explicitly escape every literal "#" (i.e. write it as "\#").
As regards whitespace, the one case where the current implementation does not always correctly infer
behaviour is where whitespace is used to separate a repetition qualifier from the atom it qualifies in a
non-"/x" regex, such as:
/ x + /
Because the module defaults to assuming that regexes always have "/x" applied, this is always interpreted
as:
/\ x+\ /x
rather than what it really is, namely:
/\ x\ +\ /
The most reliable workaround for the time being is either to always use "/x" on any regex, or never to
separate repetition qualifiers from their preceding atoms.
Multiple 'save_to' with the same target
At present, making the same file the target of two successive "save_to" requests causes the second JSON
data structure to overwrite the first.
This limitation will be removed in a subsequent release (but this will certainly involve a small change
to the structure of the JSON data that is written, even when only one "save_to" is specified).
Variable interpolations
The module handles the interpolation of strings correctly, expanding them in-place before debugging
begins.
However, it currently does not correctly handle the interpolation of "qr"'d regexes. That is, this:
use Regexp::Debugger;
my $ident = qr{ [^\W\d]\w* }x; # a qr'd regex...
$str =~ m{ ($ident) : (.*) }xms; # ...interpolated into another regex
does not work correctly...and usually will not even compile.
It is expected that this limitation will be removed in a future release, however it may only be possible
to fix the problem for more recent versions of Perl (i.e. 5.14 and later) in which the regex engine is
re-entrant.
DIAGNOSTICS
"Odd number of configuration args after "use Regexp::Debugger""
The module expects configuration arguments (see "Configuration API") to be passed as "key => value"
pairs. You passed something else.
"Unknown 'show_ws' option: %s"
The only valid options for the 'show_ws' configuration option are 'compact', 'visible', or
'original'. You specified something else (or misspelled one of the above).
"Unknown 'display' option: %s"
The only valid options for the 'display' configuration option are 'visual' or 'heatmap' or 'events'
or 'JSON'. You specified something else (or misspelled one of the above).
"Invalid 'save_to' option: %s (%s)"
The value associated with the 'save_to' option is expected to be a filehandle opened for writing, or
else a string containing the name of a file that can be opened for writing. You either passed an
unopened filehandle, an unwritable filename, or something that wasn't a plausible file.
Alternatively, if you passed a filepath, was the directory not accessible to, or writeable by, you?
"Possible typo in %s"
Prior to executing each regex, the module checks for common regex problems that can be detected
statically. For example, it looks for the two most common typos made when defining and calling
independent subpatterns. Namely: writing "(<NAME>...)" instead of "(?<NAME>...)" and "(&SUBPAT)"
instead of "(?&SUBPAT)"
To silence these warnings, just fix the typos.
Or, if the constructs are intentional, change "(<NAME>...)" to "(\<NAME>...)" and "(&SUBPAT)" to
"(\&SUBPAT)"
DEPENDENCIES
This module only works with Perl 5.10.1 and later.
The following modules are used when available:
Term::ANSIColor
Text colouring only works if this module can be loaded. Otherwise, all output will be monochromatic.
Win32::Console::ANSI
Under Windows, text colouring also requires that this module can be loaded. Otherwise, all output
will be monochromatic.
File::HomeDir
If it can't find a useful value for $ENV{HOME}, Regexp::Debugger attempts to use this module to
determine the user's home directory, in order to search for a .rxrx config file.
JSON::XS
JSON
JSON::DWIW
JSON::Syck
JSON output (i.e. for the 'save_to' option) is only possible if one of these modules can be loaded.
Otherwise, all JSON output will default to an empty "{}".
Term::ReadKey
Single-character interactions only work if this module can be loaded. Otherwise, all command
interactions will require a "<RETURN>" after them.
Time::HiRes
Autogenerated timestamps (e.g. for snapshots) will only be sub-second accurate if this module can be
loaded. Otherwise, all timestamps will only be to the nearest second.
INCOMPATIBILITIES
None reported, but this module will almost certainly not play nicely with any other that modifies regexes
using "overload::constant".
BUGS AND LIMITATIONS
No bugs have been reported.
Please report any bugs or feature requests to "bug-regexp-debugger@rt.cpan.org", or through the web
interface at <http://rt.cpan.org>.
AUTHOR
Damian Conway "<DCONWAY@CPAN.org>"
LICENCE AND COPYRIGHT
Copyright (c) 2011-2012, Damian Conway "<DCONWAY@CPAN.org>". All rights reserved.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl
itself. See perlartistic.
DISCLAIMER OF WARRANTY
BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT
PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER
PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE
SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY
OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF
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RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE
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DAMAGES.