diff --git a/btrbk b/btrbk
index 670ace8..abcd10b 100755
--- a/btrbk
+++ b/btrbk
@@ -82,104 +82,104 @@ my %config_options = (
   # NOTE: the parser always maps "no" to undef
   # NOTE: keys "volume", "subvolume" and "target" are hardcoded
   # NOTE: files "." and "no" map to <undef>
-  timestamp_format            => { default => "long",    accept => [ "short", "long", "long-iso" ], context => [ "global", "volume", "subvolume" ] },
-  snapshot_dir                => { default => undef,     accept_file => { relative => 1, absolute => 1 }, context => [ "global", "volume", "subvolume" ] },
-  snapshot_name               => { c_default => 1,       accept_file => { name_only => 1 }, context => [ "subvolume" ], deny_glob_context => 1 },   # NOTE: defaults to the subvolume name (hardcoded)
-  snapshot_create             => { default => "always",  accept => [ "no", "always", "ondemand", "onchange" ], context => [ "global", "volume", "subvolume" ] },
-  incremental                 => { default => "yes",     accept => [ "yes", "no", "strict" ] },
-  incremental_prefs           => { default => \@incremental_prefs_default, accept => qr/$incremental_prefs_match/, split => $split_match },
-  incremental_clones          => { default => "yes",     accept => [ "yes", "no" ] },
-  incremental_resolve         => { default => "mountpoint", accept => [ "mountpoint", "directory", "_all_accessible" ] },
+  timestamp_format            => { default => "long",    accept => [qw( short long long-iso )], context => [qw( global volume subvolume )] },
+  snapshot_dir                => { default => undef,     accept_file => { relative => 1, absolute => 1 }, context => [qw( global volume subvolume )] },
+  snapshot_name               => { c_default => 1,       accept_file => { name_only => 1 }, context => [qw( subvolume )], deny_glob_context => 1 },   # NOTE: defaults to the subvolume name (hardcoded)
+  snapshot_create             => { default => "always",  accept => [qw( no always ondemand onchange )], context => [qw( global volume subvolume )] },
+  incremental                 => { default => "yes",     accept => [qw( yes no strict )] },
+  incremental_prefs           => { default => \@incremental_prefs_default, accept => [ qr/$incremental_prefs_match/ ], split => $split_match },
+  incremental_clones          => { default => "yes",     accept => [qw( yes no )] },
+  incremental_resolve         => { default => "mountpoint", accept => [qw( mountpoint directory _all_accessible )] },
   preserve_day_of_week        => { default => "sunday",  accept => [ (keys %day_of_week_map) ] },
   preserve_hour_of_day        => { default => 0,         accept => [ (0..23) ]  },
-  snapshot_preserve           => { default => undef,     accept => [ "no" ], accept_preserve_matrix => 1, context => [ "global", "volume", "subvolume" ], },
-  snapshot_preserve_min       => { default => "all",     accept => [ "all", "latest", qr/[1-9][0-9]*[hdwmy]/ ], context => [ "global", "volume", "subvolume" ], },
-  target_preserve             => { default => undef,     accept => [ "no" ], accept_preserve_matrix => 1 },
-  target_preserve_min         => { default => "all",     accept => [ "all", "latest", "no", qr/[0-9]+[hdwmy]/ ] },
-  archive_preserve            => { default => undef,     accept => [ "no" ], accept_preserve_matrix => 1, context => [ "global" ] },
-  archive_preserve_min        => { default => "all",     accept => [ "all", "latest", "no", qr/[0-9]+[hdwmy]/ ], context => [ "global" ] },
-  btrfs_commit_delete         => { default => undef,     accept => [ "after", "each", "no" ] },
+  snapshot_preserve           => { default => undef,     accept => [qw( no )], accept_preserve_matrix => 1, context => [qw( global volume subvolume )], },
+  snapshot_preserve_min       => { default => "all",     accept => [qw( all latest ), qr/[1-9][0-9]*[hdwmy]/ ], context => [qw( global volume subvolume )], },
+  target_preserve             => { default => undef,     accept => [qw( no )], accept_preserve_matrix => 1 },
+  target_preserve_min         => { default => "all",     accept => [qw( all latest no ), qr/[0-9]+[hdwmy]/ ] },
+  archive_preserve            => { default => undef,     accept => [qw( no )], accept_preserve_matrix => 1, context => [qw( global )] },
+  archive_preserve_min        => { default => "all",     accept => [qw( all latest no ), qr/[0-9]+[hdwmy]/ ], context => [qw( global )] },
+  btrfs_commit_delete         => { default => undef,     accept => [qw( after each no )] },
   ssh_identity                => { default => undef,     accept_file => { absolute => 1 } },
   ssh_user                    => { default => "root",    accept => [ qr/[a-z_][a-z0-9_-]*/ ] },
-  ssh_compression             => { default => undef,     accept => [ "yes", "no" ] },
+  ssh_compression             => { default => undef,     accept => [qw( yes no )] },
   ssh_cipher_spec             => { default => "default", accept => [ qr/$ssh_cipher_match(,$ssh_cipher_match)*/ ] },
-  transaction_log             => { default => undef,     accept => [ "no" ], accept_file => { absolute => 1 }, context => [ "global" ] },
-  transaction_syslog          => { default => undef,     accept => [ "no", @syslog_facilities ], context => [ "global" ] },
-  lockfile                    => { default => undef,     accept => [ "no" ], accept_file => { absolute => 1 }, context => [ "global" ] },
+  transaction_log             => { default => undef,     accept => [qw( no )], accept_file => { absolute => 1 }, context => [qw( global )] },
+  transaction_syslog          => { default => undef,     accept => [qw( no ), @syslog_facilities ], context => [qw( global )] },
+  lockfile                    => { default => undef,     accept => [qw( no )], accept_file => { absolute => 1 }, context => [qw( global )] },
 
-  rate_limit                  => { default => undef,     accept => [ "no", qr/[0-9]+[kmgtKMGT]?/ ], require_bin => 'mbuffer' },
-  rate_limit_remote           => { default => undef,     accept => [ "no", qr/[0-9]+[kmgtKMGT]?/ ] },  # NOTE: requires 'mbuffer' command on remote hosts
-  stream_buffer               => { default => undef,     accept => [ "no", qr/[0-9]+[kmgKMG%]?/  ], require_bin => 'mbuffer' },
-  stream_buffer_remote        => { default => undef,     accept => [ "no", qr/[0-9]+[kmgKMG%]?/  ] },  # NOTE: requires 'mbuffer' command on remote hosts
-  stream_compress             => { default => undef,     accept => [ "no", (keys %compression) ] },
-  stream_compress_level       => { default => "default", accept => [ "default", qr/[0-9]+/ ] },
-  stream_compress_long        => { default => "default", accept => [ "default", qr/[0-9]+/ ] },
-  stream_compress_threads     => { default => "default", accept => [ "default", qr/[0-9]+/ ] },
-  stream_compress_adapt       => { default => undef,     accept => [ "yes", "no" ] },
+  rate_limit                  => { default => undef,     accept => [qw( no ), qr/[0-9]+[kmgtKMGT]?/ ], require_bin => 'mbuffer' },
+  rate_limit_remote           => { default => undef,     accept => [qw( no ), qr/[0-9]+[kmgtKMGT]?/ ] },  # NOTE: requires 'mbuffer' command on remote hosts
+  stream_buffer               => { default => undef,     accept => [qw( no ), qr/[0-9]+[kmgKMG%]?/  ], require_bin => 'mbuffer' },
+  stream_buffer_remote        => { default => undef,     accept => [qw( no ), qr/[0-9]+[kmgKMG%]?/  ] },  # NOTE: requires 'mbuffer' command on remote hosts
+  stream_compress             => { default => undef,     accept => [qw( no ), (keys %compression) ] },
+  stream_compress_level       => { default => "default", accept => [qw( default ), qr/[0-9]+/ ] },
+  stream_compress_long        => { default => "default", accept => [qw( default ), qr/[0-9]+/ ] },
+  stream_compress_threads     => { default => "default", accept => [qw( default ), qr/[0-9]+/ ] },
+  stream_compress_adapt       => { default => undef,     accept => [qw( yes no )] },
 
-  raw_target_compress         => { default => undef,     accept => [ "no", (keys %compression) ] },
-  raw_target_compress_level   => { default => "default", accept => [ "default", qr/[0-9]+/ ] },
-  raw_target_compress_long    => { default => "default", accept => [ "default", qr/[0-9]+/ ] },
-  raw_target_compress_threads => { default => "default", accept => [ "default", qr/[0-9]+/ ] },
-  raw_target_encrypt          => { default => undef,     accept => [ "no", "gpg", "openssl_enc" ] },
+  raw_target_compress         => { default => undef,     accept => [qw( no ), (keys %compression) ] },
+  raw_target_compress_level   => { default => "default", accept => [qw( default ), qr/[0-9]+/ ] },
+  raw_target_compress_long    => { default => "default", accept => [qw( default ), qr/[0-9]+/ ] },
+  raw_target_compress_threads => { default => "default", accept => [qw( default ), qr/[0-9]+/ ] },
+  raw_target_encrypt          => { default => undef,     accept => [qw( no gpg openssl_enc )] },
   raw_target_block_size       => { default => "128K",    accept => [ qr/[0-9]+[kmgKMG]?/ ] },
-  raw_target_split            => { default => undef,     accept => [ "no", qr/[0-9]+([kmgtpezyKMGTPEZY][bB]?)?/ ] },
+  raw_target_split            => { default => undef,     accept => [qw( no ), qr/[0-9]+([kmgtpezyKMGTPEZY][bB]?)?/ ] },
   gpg_keyring                 => { default => undef,     accept_file => { absolute => 1 } },
   gpg_recipient               => { default => undef,     accept => [ qr/[0-9a-zA-Z_@\+\-\.]+/ ] },
   openssl_ciphername          => { default => "aes-256-cbc", accept => [ qr/[0-9a-zA-Z\-]+/ ] },
-  openssl_iv_size             => { default => undef,     accept => [ "no", qr/[0-9]+/ ] },
+  openssl_iv_size             => { default => undef,     accept => [qw( no ), qr/[0-9]+/ ] },
   openssl_keyfile             => { default => undef,     accept_file => { absolute => 1 } },
 
   kdf_backend                 => { default => undef,     accept_file => { absolute => 1 } },
   kdf_keysize                 => { default => "32",      accept => [ qr/[0-9]+/ ] },
-  kdf_keygen                  => { default => "once",    accept => [ "once", "each" ] },
+  kdf_keygen                  => { default => "once",    accept => [qw( once each )] },
 
   group                       => { default => undef,     accept => [ qr/$group_match/ ], allow_multiple => 1, split => $split_match },
-  noauto                      => { default => undef,     accept => [ "yes", "no" ] },
+  noauto                      => { default => undef,     accept => [qw( yes no )] },
 
-  backend                     => { default => "btrfs-progs", accept => [       "btrfs-progs", "btrfs-progs-btrbk", "btrfs-progs-sudo", "btrfs-progs-doas" ] },
-  backend_local               => { default => undef,         accept => [ "no", "btrfs-progs", "btrfs-progs-btrbk", "btrfs-progs-sudo", "btrfs-progs-doas" ] },
-  backend_remote              => { default => undef,         accept => [ "no", "btrfs-progs", "btrfs-progs-btrbk", "btrfs-progs-sudo", "btrfs-progs-doas" ] },
-  backend_local_user          => { default => undef,         accept => [ "no", "btrfs-progs", "btrfs-progs-btrbk", "btrfs-progs-sudo", "btrfs-progs-doas" ] },
+  backend                     => { default => "btrfs-progs", accept => [qw(    btrfs-progs btrfs-progs-btrbk btrfs-progs-sudo btrfs-progs-doas )] },
+  backend_local               => { default => undef,         accept => [qw( no btrfs-progs btrfs-progs-btrbk btrfs-progs-sudo btrfs-progs-doas )] },
+  backend_remote              => { default => undef,         accept => [qw( no btrfs-progs btrfs-progs-btrbk btrfs-progs-sudo btrfs-progs-doas )] },
+  backend_local_user          => { default => undef,         accept => [qw( no btrfs-progs btrfs-progs-btrbk btrfs-progs-sudo btrfs-progs-doas )] },
 
-  compat                      => { default => undef,     accept => [ "no", "busybox" ] },
-  compat_local                => { default => undef,     accept => [ "no", "busybox" ] },
-  compat_remote               => { default => undef,     accept => [ "no", "busybox" ] },
-  safe_commands               => { default => undef,     accept => [ "yes", "no" ], context => [ "global" ] },
+  compat                      => { default => undef,     accept => [qw( no busybox )] },
+  compat_local                => { default => undef,     accept => [qw( no busybox )] },
+  compat_remote               => { default => undef,     accept => [qw( no busybox )] },
+  safe_commands               => { default => undef,     accept => [qw( yes no )], context => [qw( global )] },
 
-  snapshot_qgroup_destroy     => { default => undef,     accept => [ "yes", "no" ], context => [ "global", "volume", "subvolume" ] },
-  target_qgroup_destroy       => { default => undef,     accept => [ "yes", "no" ] },
-  archive_qgroup_destroy      => { default => undef,     accept => [ "yes", "no" ], context => [ "global" ] },
+  snapshot_qgroup_destroy     => { default => undef,     accept => [qw( yes no )], context => [qw( global volume subvolume )] },
+  target_qgroup_destroy       => { default => undef,     accept => [qw( yes no )] },
+  archive_qgroup_destroy      => { default => undef,     accept => [qw( yes no )], context => [qw( global )] },
 
-  archive_exclude             => { default => undef,     accept_file => { wildcards => 1 }, allow_multiple => 1, context => [ "global" ] },
-  archive_exclude_older       => { default => undef,     accept => [ "yes", "no" ] },
+  archive_exclude             => { default => undef,     accept_file => { wildcards => 1 }, allow_multiple => 1, context => [qw( global )] },
+  archive_exclude_older       => { default => undef,     accept => [qw( yes no )] },
 
-  cache_dir                   => { default => undef,     accept_file => { absolute => 1 }, allow_multiple => 1, context => [ "global" ] },
-  ignore_extent_data_inline   => { default => "yes",     accept => [ "yes", "no" ] },
+  cache_dir                   => { default => undef,     accept_file => { absolute => 1 }, allow_multiple => 1, context => [qw( global )] },
+  ignore_extent_data_inline   => { default => "yes",     accept => [qw( yes no )] },
 
-  warn_unknown_targets        => { default => undef,     accept => [ "yes", "no" ] },
+  warn_unknown_targets        => { default => undef,     accept => [qw( yes no )] },
 
   # deprecated options
-  ssh_port                    => { default => "default", accept => [ "default", qr/[0-9]+/ ],
+  ssh_port                    => { default => "default", accept => [qw( default ), qr/[0-9]+/ ],
                                    deprecated => { DEFAULT => { warn => 'Please use "ssh://hostname[:port]" notation in the "volume" and "target" configuration lines.' } } },
-  btrfs_progs_compat          => { default => undef, accept => [ "yes", "no" ],
+  btrfs_progs_compat          => { default => undef, accept => [qw( yes no )],
                                    deprecated => { DEFAULT => { ABORT => 1, warn => 'This feature has been dropped in btrbk-v0.23.0. Please update to newest btrfs-progs, AT LEAST >= $BTRFS_PROGS_MIN' } } },
-  snapshot_preserve_daily     => { default => 'all', accept => [ "all", qr/[0-9]+/ ], context => [ "global", "volume", "subvolume" ],
+  snapshot_preserve_daily     => { default => 'all', accept => [qw( all ), qr/[0-9]+/ ], context => [qw( global volume subvolume )],
                                    deprecated => { DEFAULT => { FAILSAFE_PRESERVE => 1, warn => 'Please use "snapshot_preserve" and/or "snapshot_preserve_min"' } } },
-  snapshot_preserve_weekly    => { default => 0, accept => [ "all", qr/[0-9]+/ ], context => [ "global", "volume", "subvolume" ],
+  snapshot_preserve_weekly    => { default => 0, accept => [qw( all ), qr/[0-9]+/ ], context => [qw( global volume subvolume )],
                                    deprecated => { DEFAULT => { FAILSAFE_PRESERVE => 1, warn => 'Please use "snapshot_preserve" and/or "snapshot_preserve_min"' } } },
-  snapshot_preserve_monthly   => { default => 'all', accept => [ "all", qr/[0-9]+/ ], context => [ "global", "volume", "subvolume" ],
+  snapshot_preserve_monthly   => { default => 'all', accept => [qw( all ), qr/[0-9]+/ ], context => [qw( global volume subvolume )],
                                    deprecated => { DEFAULT => { FAILSAFE_PRESERVE => 1, warn => 'Please use "snapshot_preserve" and/or "snapshot_preserve_min"' } } },
-  target_preserve_daily       => { default => 'all', accept => [ "all", qr/[0-9]+/ ],
+  target_preserve_daily       => { default => 'all', accept => [qw( all ), qr/[0-9]+/ ],
                                    deprecated => { DEFAULT => { FAILSAFE_PRESERVE => 1, warn => 'Please use "target_preserve" and/or "target_preserve_min"' } } },
-  target_preserve_weekly      => { default => 0, accept => [ "all", qr/[0-9]+/ ],
+  target_preserve_weekly      => { default => 0, accept => [qw( all ), qr/[0-9]+/ ],
                                    deprecated => { DEFAULT => { FAILSAFE_PRESERVE => 1, warn => 'Please use "target_preserve" and/or "target_preserve_min"' } } },
-  target_preserve_monthly     => { default => 'all', accept => [ "all", qr/[0-9]+/ ],
+  target_preserve_monthly     => { default => 'all', accept => [qw( all ), qr/[0-9]+/ ],
                                    deprecated => { DEFAULT => { FAILSAFE_PRESERVE => 1, warn => 'Please use "target_preserve" and/or "target_preserve_min"' } } },
-  resume_missing              => { default => "yes", accept => [ "yes", "no" ],
+  resume_missing              => { default => "yes", accept => [qw( yes no )],
                                    deprecated => { yes => { warn => 'ignoring (missing backups are always resumed since btrbk v0.23.0)' },
                                                    no  => { FAILSAFE_PRESERVE => 1, warn => 'Please use "target_preserve_min latest" and "target_preserve no" if you want to keep only the latest backup', } } },
-  snapshot_create_always      => { default => undef, accept => [ "yes", "no" ],
+  snapshot_create_always      => { default => undef, accept => [qw( yes no )],
                                    deprecated => { yes => { warn => "Please use \"snapshot_create always\"",
                                                             replace_key   => "snapshot_create",
                                                             replace_value => "always",
@@ -190,7 +190,7 @@ my %config_options = (
                                                            }
                                                   },
                                  },
-  receive_log                 => { default => undef, accept => [ "sidecar", "no" ], accept_file => { absolute => 1 },
+  receive_log                 => { default => undef, accept => [qw( sidecar no )], accept_file => { absolute => 1 },
                                    deprecated => { DEFAULT => { warn => "ignoring" } },
                                  }
  );