double-quote.pl

use 5.010;
use strict;
use warnings;

use Marpa::R2;
use YAML;

my $g = Marpa::R2::Scanless::G->new( { 
    source => \(<<'END_OF_SOURCE'),
:default ::= action => [name, value]
lexeme default = action => [name, value] latm => 1

    S         ::= quote text quote

    text      ::= in_quotes+
    in_quotes ::= non_quote | escaped_quote

    quote           ~ '"';
    non_quote       ~ [^"\\]+ # "
    escaped_quote   ~ '\"'

:discard ~ whitespace
whitespace ~ [\s]+
END_OF_SOURCE
} );

my $input = <<EOI;
"before escaped quotes \\"in escaped quotes\\" after escaped quotes \\"again in escaped quotes\\" and some text again"
EOI

my $r = Marpa::R2::Scanless::R->new( { grammar => $g, trace_terminals => 1 } );
eval {$r->read(\$input)} || die "\nParse failure, progress report is:\n" . $r->show_progress;
say Dump ${ $r->value };

- S
-
  - quote
  - '"'
-
  - text
  -
    - in_quotes
    -
      - non_quote
      - 'before escaped quotes '
  -
    - in_quotes
    -
      - escaped_quote
      - \"
  -
    - in_quotes
    -
      - non_quote
      - in escaped quotes
  -
    - in_quotes
    -
      - escaped_quote
      - \"
  -
    - in_quotes
    -
      - non_quote
      - ' after escaped quotes '
  -
    - in_quotes
    -
      - escaped_quote
      - \"
  -
    - in_quotes
    -
      - non_quote
      - again in escaped quotes
  -
    - in_quotes
    -
      - escaped_quote
      - \"
  -
    - in_quotes
    -
      - non_quote
      - ' and some text again'
-
  - quote
  - '"'