I'm just wondering if I discovered some kind of bug, or if I'm actually doing something wrong.

Here's a test script to illustrate.

#!/usr/bin/perl

use strict;
use warnings;

use YAML::Any qw(DumpFile LoadFile);

my $yaml_file = 'test-re.yaml';

my @default_patterns = (
    qr/^foo.*bar.*baz/i,
    qr/^bar.*baz.*quux/i,
    qr/^quux$/,
);


my $yaml = {};

if ( -w $yaml_file ) {
    $yaml = LoadFile( $yaml_file );
}


if ( scalar @ARGV ) {
    push @{$yaml->{patterns}}, qr/$_/ for @ARGV;
} else {

    # If no args, assume we want a fresh pattern dump, seed
    # with the default list of patterns.
    #
    $yaml->{patterns} = [];
    push @{$yaml->{patterns}}, $_ for @default_patterns;
}


DumpFile( $yaml_file, $yaml )
    or die "Error writing yaml file: $!\n";

print "Wrote $yaml_file\n";
[download]

Here's the output from my shell as I use my test script.

$ ls test-re.yaml
ls: cannot access test-re.yaml: No such file or directory

$ test-yaml-re.pl
Wrote test-re.yaml

$ cat test-re.yaml
---
patterns:
  - !!perl/regexp (?^i:^foo.*bar.*baz)
  - !!perl/regexp (?^i:^bar.*baz.*quux)
  - !!perl/regexp (?^:^quux$)

$ test-yaml-re.pl '^foo$'
Wrote test-re.yaml

$ cat test-re.yaml
---
patterns:
  - !!perl/regexp (?^:(?^i:^foo.*bar.*baz))
  - !!perl/regexp (?^:(?^i:^bar.*baz.*quux))
  - !!perl/regexp (?^:(?^:^quux$))
  - !!perl/regexp (?^:^foo$)

$ test-yaml-re.pl '^bar$'
Wrote test-re.yaml

$ cat test-re.yaml
---
patterns:
  - !!perl/regexp (?^:(?^:(?^i:^foo.*bar.*baz)))
  - !!perl/regexp (?^:(?^:(?^i:^bar.*baz.*quux)))
  - !!perl/regexp (?^:(?^:(?^:^quux$)))
  - !!perl/regexp (?^:(?^:^foo$))
  - !!perl/regexp (?^:^bar$)

$ test-yaml-re.pl '^baz$'
Wrote test-re.yaml

$ cat test-re.yaml
---
patterns:
  - !!perl/regexp (?^:(?^:(?^:(?^i:^foo.*bar.*baz))))
  - !!perl/regexp (?^:(?^:(?^:(?^i:^bar.*baz.*quux))))
  - !!perl/regexp (?^:(?^:(?^:(?^:^quux$))))
  - !!perl/regexp (?^:(?^:(?^:^foo$)))
  - !!perl/regexp (?^:(?^:^bar$))
  - !!perl/regexp (?^:^baz$)
[download]

So, every time I add a single qr quoted pattern to the yaml file, it's like it's nesting everything above it, even though it's not like I'm rerunning the qr quoting on every value in the list.

I discovered this while changing one of my scripts where I'm comparing a value to a list of patterns with the smart match operator: if ( $_ ~~ @patterns )

Also, I didn't think of it til just before I was going to submit this post, I added a line to the test script to display the result of YAML::Any->implementation and it showed YAML::Syck to be the selected version. The problem occurs on perl-5.14.2 with YAML::Syck 1.19 as well as perl-5.16.0 with YAML::Syck 1.20.