YAML::Tiny clearly states that it only implements a subset of features, but as far as I understand YAML and YAML::XS are supposed to be drop-in replacements of each other. YAML::Any is a wrapper around several YAML processors, though at one point YAML itself will be promoted to do that job.

Yet, when I tried to switch from YAML to YAML::XS I've encountered two cases of incompatibility. Probably in both cases the YAML file wasn't according to the specs, but in both cases YAML was forgiving and parsed the files as I expected them and in both cases YAML::XS threw exception. I've created minimal examples for both cases and I have tried to parse them with the following:

• YAML version 1.15
• YAML::XS version 0.59
• YAML::Tiny version 1.69
• YAML::Syck version 1.29

Space required after :

The YAML file:

examples/files/space_required.yml

x:
  'a': 'a'
  'b':'b'

perl yaml.pl files/space_required.yml parsed and created

$VAR1 = {
          'x' => {
                 'a' => 'a',
                 'b' => 'b'
               }
        };

perl yaml_xs.pl files/space_required.yml

YAML::XS::Load Error: The problem:

    could not find expected ':'

was found at document: 1, line: 4, column: 1
while scanning a simple key at line: 3, column: 3

perl yaml_tiny.pl files/space_required.yml threw exception:

YAML::Tiny failed to classify line '  'b':'b'' at yaml_tiny.pl line 11.

perl yaml_syck.pl files/space_required.yml threw exception:

Syck parser (line 4, column -1): syntax error 

The solution here is to put a space after the : in the line of 'b' as in the following:

examples/files/space_required_solved.yml

x:
  'a': 'a'
  'b': 'b'

I am not sure if this is something that needs to be fixed in the YAML module, or just documented, but I've opened a ticket.

Value with : needs to be quoted

The YAML file:

examples/files/quote_colon.yml

a:
  - b: c:

perl yaml.pl files/quote_colon.yml properly parses the YAML file and generates this data structure:

$VAR1 = {
          'a' => [
                 {
                   'b' => 'c:'
                 }
               ]
        };

perl yaml_xs.pl files/quote_colon.yml throws exception:

YAML::XS::Load Error: The problem:

    mapping values are not allowed in this context

was found at document: 1, line: 2, column: 9

perl yaml_tiny.pl files/quote_colon.yml throws exception:

YAML::Tiny found illegal characters in plain scalar: 'c:' at yaml_tiny.pl line 11.

perl yaml_syck.pl files/quote_colon.yml throws exception:

Syck parser (line 2, column 9): syntax error

The solution here is to put the value with the : in it between single-quote marks:

examples/files/quote_colon_solved.yml

a:
  - b: 'c:'

Here too I've opened a ticket for consideration.

The scripts I used

examples/yaml.pl

use 5.010;
use strict;
use warnings;

use Data::Dumper qw(Dumper);
use YAML;

my $file = shift or die "Usage: $0 YAML_FILE\n";

say $YAML::VERSION;
my $x = YAML::LoadFile($file);
say Dumper $x; 

examples/yaml_xs.pl

use 5.010;
use strict;
use warnings;

use Data::Dumper qw(Dumper);
use YAML::XS;

my $file = shift or die "Usage: $0 YAML_FILE\n";

say $YAML::XS::VERSION;
my $x = YAML::XS::LoadFile($file);
say Dumper $x; 

examples/yaml_tiny.pl

use 5.010;
use strict;
use warnings;

use Data::Dumper qw(Dumper);
use YAML::Tiny;

my $file = shift or die "Usage: $0 YAML_FILE\n";

say $YAML::Tiny::VERSION;
my $x = YAML::Tiny::LoadFile($file);
say Dumper $x; 

examples/yaml_syck.pl

use 5.010;
use strict;
use warnings;

use Data::Dumper qw(Dumper);
use YAML::Syck;

my $file = shift or die "Usage: $0 YAML_FILE\n";

say $YAML::Syck::VERSION;
my $x = YAML::Syck::LoadFile($file);
say Dumper $x;