Indented Here Documents

 <<~EOD
     How doth the little crocodile
     Improve his shining tail
     EOD

will have the three indentations represented by whitespace objects and each line of the literal represented by its own string object, but

 <<~EOD
 How doth the little crocodile
 Improve his shining tail
 EOD

will parse the same as the non-indented version, except for the addition of the token representing the '~'.

PPI is ahead of this module, and recognized indented here documents as of its version 1.246 (May 2019). Unfortunately, as of version 1.270 the indent gets lost in the parse, so a "PPIx::QuoteLike" object initialized from such a PPI::Token::HereDoc will be seen as having an indentation of '' regardless of the actual indentation in the source. I believe this restriction will go away when <https://github.com/Perl-Critic/PPI/issues/251> is resolved.

new

 my $str = PPIx::QuoteLike->new( $source, %arg );

This static method parses the argument, and returns a new object containing the parse. The $source argument can be either a scalar or an appropriate PPI::Element object.

If the $source argument is a scalar, it is presumed to represent a quote-like literal of some sort, provided it begins like one. Otherwise this method will return nothing. The scalar representation of a here document is a multi-line string whose first line consists of the leading " << " and the start delimiter, and whose subsequent lines consist of the content of the here document and the end delimiter. Indented here documents were not supported by this class until version 0.015.

"PPI" classes that can be handled are PPI::Token::Quote, PPI::Token::QuoteLike::Backtick, PPI::Token::QuoteLike::Command, PPI::Token::QuoteLike::Readline, and PPI::Token::HereDoc. Any other object will cause "new()" to return nothing.

Additional optional arguments can be passed as name/value pairs. Supported arguments are:

encoding

This is the encoding of the $source. If this is specified as something other than "undef", the $source will be decoded before processing.

If the $source is a "PPI::Element", this encoding is used only if the document that contains the element has neither a byte order mark nor 'use utf8'.

index_locations

This Boolean argument determines whether the locations of the tokens should be computed. It defaults to true if the $source argument is a PPI::Element or if the "location" argument was provided, and false otherwise.

location

This argument is a reference to an array compatible with that returned by the PPI::Element location() method. It defaults to the location of the $source argument if that was a PPI::Element, otherwise no locations will be available.

postderef

THIS ARGUMENT IS DEPRECATED. See DEPRECATION NOTICE above for the details.

This Boolean argument determines whether postfix dereferencing is recognized in interpolation. If unspecified, or specified as "undef", it defaults to true. In version 0.012 it defaulted to the value of $PPIx::QuoteLike::DEFAULT_POSTDEREF. This variable was not exported, and was true by default.

trace

This Boolean argument causes a trace of the parse to be written to standard out. Setting this to a true value is unsupported in the sense that the author makes no representation as to what will happen if you do it, and reserves the right to make changes to the functionality, or retract it completely, without notice.

All other arguments are unsupported and reserved to the author.

child

 my $kid = $str->child( 0 );

This method returns the child element whose index is given as the argument. Children do not include the type(), or the start() or finish() delimiters. Negative indices are valid, and given the usual Perl interpretation.

children

 my @kids = $str->children();

This method returns all child elements. Children do not include the type(), or the start() or finish() delimiters.

column_number

content

 say $str->content();

This method returns the content of the object. If the original argument was a valid Perl string, this should be the same as the originally-parsed string.

delimiters

 say $str->delimiters();

This method returns the delimiters of the object, as a string. This will be two characters unless the argument to new() was a here document, missing its end delimiter, or an invalid string. In the latter case the return might be anything.

elements

 my @elem = $str->elements();

This method returns all elements of the object. This includes type(), start(), children(), and finish(), in that order.

failures

 say $str->failures();

This method returns the number of parse failures found. These are instances where the parser could not figure out what was going on, and should be the same as the number of PPIx::QuoteLike::Token::Unknown objects returned by elements().

find

 for ( @{[ $str->find( $criteria ) || [] } ) {
     ...
 }

This method finds and returns a reference to an array of all elements that meet the given criteria. If nothing is found, a false value is returned.

The $criteria can be either the name of a PPIx::QuoteLike::Token class, or a code reference. In the latter case, the code is called for each element in elements(), with the element as the only argument. The element is included in the output if the code returns a true value.

finish

 say map { $_->content() } $str->finish();

This method returns the finishing elements of the parse. It is actually an array, with the first element being a PPIx::QuoteLike::Token::Delimiter. If the parse is of a here document there will be a second element, which will be a PPIx::QuoteLike::Token::Whitespace containing the trailing new line character.

If called in list context you get the whole array. If called in scalar context you get the element whose index is given in the argument, or element zero if no argument is specified.

handles

 say PPIx::QuoteLike->handles( $string ) ?
     "We can handle $string" :
     "We can not handle $string";

This convenience static method returns a true value if this package can be expected to handle the content of $string (be it scalar or object), and a false value otherwise.

indentation

Note that if indented syntax is used but the here document is not in fact indented, this will return '', which evaluates to false.

interpolates

 say $str->interpolates() ?
     'The string interpolates' :
     'The string does not interpolate';

This method returns a true value if the parsed string interpolates, and a false value if it does not. This does not indicate whether any interpolation actually takes place, only whether the string is double-quotish or single-quotish.

line_number

location

The array is compatible with the corresponding PPI::Element method.

logical_filename

logical_line_number

parent

perl_version_introduced

perl_version_removed

schild

 my $skid = $str->schild( 0 );

This method returns the significant child elements whose index is given by the argument. Negative indices are interpreted in the usual way.

schildren

 my @skids = $str->schildren();

This method returns the significant children.

source

 my $source = $str->source();

This method returns the $source argument to new(), whatever it was.

start

 say map { $_->content() } $str->start();

This method returns the starting elements of the parse. It is actually an array, with the first element being a PPIx::QuoteLike::Token::Delimiter. If the parse is of a here document there will be a second element, which will be a PPIx::QuoteLike::Token::Whitespace containing the trailing new line character.

If called in list context you get the whole array. If called in scalar context you get the element whose index is given in the argument, or element zero if no argument is specified.

statement

In general this method will return something only under the following conditions:

• The string is contained in a PPIx::QuoteLike object;
• That object was initialized from a PPI::Element;
• The PPI::Element is contained in a statement.

top

type

 my $type = $str->type();

This method returns the type object. This will be a PPIx::QuoteLike::Token::Structure if the parse was successful; otherwise it might be "undef". Its contents will be everything up to the start delimiter, and will typically be 'q', 'qq', 'qx', '<<' (for here documents), or '' (for quoted strings).

The type data are actually an array. If the second element is present it will be the white space (if any) separating the actual type from the value. If called in list context you get the whole array. If called in scalar context you get the element whose index is given in the argument, or element zero if no argument is specified.

variables

 say "Interpolates $_" for $str->variables();

NOTE that this method is discouraged, and may well be deprecated and removed. My problem with it is that it returns variable names rather than PPI::Element objects, leaving you no idea how the variables are used. It was originally written for the benefit of Perl::Critic::Policy::Variables::ProhibitUnusedVarsStricter, but has proven inadequate to that policy's needs.

This convenience method returns all interpolated variables. Each is returned only once, and they are returned in no particular order. If the object does not represent a string that interpolates, nothing is returned.

visual_column_number

Changes in Syntax

 $ perl -le 'print "Foo\FBar"'

prints "FooFBar" under Perl 5.14.4, but "Foobar" under 5.16.0. "PPIx::QuoteLike" generally assumes the more modern parse in cases like this.

Static Parsing

Nevertheless, this class is trying to statically parse quote-like things. I do not have any examples of where the parse of a quote-like thing would change based on what is interpolated, but neither can I rule it out. Caveat user.

PPI Restrictions

Non-Standard Syntax

Acme::PerlML, which renders Perl as XML.

"Data::PostfixDeref", which causes Perl to interpret suffixed empty brackets as dereferencing the thing they suffix. This module by Ben Morrow ("BMORROW") appears to have been retracted.

Filter::Trigraph, which recognizes ANSI C trigraphs, allowing Perl to be written in the ISO 646 character set.

Perl6::Pugs. Enough said.