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As we're using Parser.pm at my company (with the proper copyright notice, I might add) and I've started writing tests for it. Things have gone well until I encountered a case with &concatenate which doesn't match my expectations. Are my expectations wrong or is this a bug?

Below is a minimal test case demonstrating the problem. This assumes Stream.pm and Parser.pm are in the same directory as this script:

  #!/usr/bin/perl
  use strict;
  use warnings;

  use lib '.';

  use Stream qw/node list_to_stream/;
  use Parser ':all';
    
  use Test::More 'no_plan';

  my @tokens = ( 
    node( OP  => '+' ),
    node( VAR => 'x' ), 
    node( VAL =>  3  )
  );  
  my $stream = list_to_stream(@tokens);

  my $parser = concatenate( 
    lookfor('OP'), 
    lookfor('VAR'),
  );
  my ( $parsed, $remainder ) = $parser->($stream);
  is_deeply $parsed, [qw/+ x/],
    'concatenate should return the parsed values';
  is_deeply $remainder, [ VAL => 3 ],
    '... and the rest of the stream';

  # the next test fails ...
  $parser = concatenate(
    lookfor('OP'),
    lookfor('VAR'),
    lookfor('VAL'),
  );
  ( $parsed, $remainder ) = $parser->($stream);
  is_deeply $parsed, [qw/+ x 3/],
    'concatenate should return the parsed values';
  ok !defined $remainder,
    '... and the remaining stream should be empty';
[download]

When I try to concatenate just the first two tokens, everything is fine. However, the if I try and concatenate all of the tokens together, the parser fails to find a match.

I'm sure I can fix this, but I want to make sure this is really a bug and not me misunderstanding how this code is supposed to work. I seached the errata but couldn't find and example of this problem.

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