/usr/share/perl5/YAML/Error.pm is in libyaml-perl 1.24-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 | package YAML::Error;
use YAML::Mo;
has 'code';
has 'type' => default => sub {'Error'};
has 'line';
has 'document';
has 'arguments' => default => sub {[]};
my ($error_messages, %line_adjust);
sub format_message {
    my $self = shift;
    my $output = 'YAML ' . $self->type . ': ';
    my $code = $self->code;
    if ($error_messages->{$code}) {
        $code = sprintf($error_messages->{$code}, @{$self->arguments});
    }
    $output .= $code . "\n";
    $output .= '   Code: ' . $self->code . "\n"
        if defined $self->code;
    $output .= '   Line: ' . $self->line . "\n"
        if defined $self->line;
    $output .= '   Document: ' . $self->document . "\n"
        if defined $self->document;
    return $output;
}
sub error_messages {
    $error_messages;
}
%$error_messages = map {s/^\s+//;s/\\n/\n/;$_} split "\n", <<'...';
YAML_PARSE_ERR_BAD_CHARS
  Invalid characters in stream. This parser only supports printable ASCII
YAML_PARSE_ERR_BAD_MAJOR_VERSION
  Can't parse a %s document with a 1.0 parser
YAML_PARSE_WARN_BAD_MINOR_VERSION
  Parsing a %s document with a 1.0 parser
YAML_PARSE_WARN_MULTIPLE_DIRECTIVES
  '%s directive used more than once'
YAML_PARSE_ERR_TEXT_AFTER_INDICATOR
  No text allowed after indicator
YAML_PARSE_ERR_NO_ANCHOR
  No anchor for alias '*%s'
YAML_PARSE_ERR_NO_SEPARATOR
  Expected separator '---'
YAML_PARSE_ERR_SINGLE_LINE
  Couldn't parse single line value
YAML_PARSE_ERR_BAD_ANCHOR
  Invalid anchor
YAML_DUMP_ERR_INVALID_INDENT
  Invalid Indent width specified: '%s'
YAML_LOAD_USAGE
  usage: YAML::Load($yaml_stream_scalar)
YAML_PARSE_ERR_BAD_NODE
  Can't parse node
YAML_PARSE_ERR_BAD_EXPLICIT
  Unsupported explicit transfer: '%s'
YAML_DUMP_USAGE_DUMPCODE
  Invalid value for DumpCode: '%s'
YAML_LOAD_ERR_FILE_INPUT
  Couldn't open %s for input:\n%s
YAML_DUMP_ERR_FILE_CONCATENATE
  Can't concatenate to YAML file %s
YAML_DUMP_ERR_FILE_OUTPUT
  Couldn't open %s for output:\n%s
YAML_DUMP_ERR_FILE_OUTPUT_CLOSE
  Error closing %s:\n%s
YAML_DUMP_ERR_NO_HEADER
  With UseHeader=0, the node must be a plain hash or array
YAML_DUMP_WARN_BAD_NODE_TYPE
  Can't perform serialization for node type: '%s'
YAML_EMIT_WARN_KEYS
  Encountered a problem with 'keys':\n%s
YAML_DUMP_WARN_DEPARSE_FAILED
  Deparse failed for CODE reference
YAML_DUMP_WARN_CODE_DUMMY
  Emitting dummy subroutine for CODE reference
YAML_PARSE_ERR_MANY_EXPLICIT
  More than one explicit transfer
YAML_PARSE_ERR_MANY_IMPLICIT
  More than one implicit request
YAML_PARSE_ERR_MANY_ANCHOR
  More than one anchor
YAML_PARSE_ERR_ANCHOR_ALIAS
  Can't define both an anchor and an alias
YAML_PARSE_ERR_BAD_ALIAS
  Invalid alias
YAML_PARSE_ERR_MANY_ALIAS
  More than one alias
YAML_LOAD_ERR_NO_CONVERT
  Can't convert implicit '%s' node to explicit '%s' node
YAML_LOAD_ERR_NO_DEFAULT_VALUE
  No default value for '%s' explicit transfer
YAML_LOAD_ERR_NON_EMPTY_STRING
  Only the empty string can be converted to a '%s'
YAML_LOAD_ERR_BAD_MAP_TO_SEQ
  Can't transfer map as sequence. Non numeric key '%s' encountered.
YAML_DUMP_ERR_BAD_GLOB
  '%s' is an invalid value for Perl glob
YAML_DUMP_ERR_BAD_REGEXP
  '%s' is an invalid value for Perl Regexp
YAML_LOAD_ERR_BAD_MAP_ELEMENT
  Invalid element in map
YAML_LOAD_WARN_DUPLICATE_KEY
  Duplicate map key '%s' found. Ignoring.
YAML_LOAD_ERR_BAD_SEQ_ELEMENT
  Invalid element in sequence
YAML_PARSE_ERR_INLINE_MAP
  Can't parse inline map
YAML_PARSE_ERR_INLINE_SEQUENCE
  Can't parse inline sequence
YAML_PARSE_ERR_BAD_DOUBLE
  Can't parse double quoted string
YAML_PARSE_ERR_BAD_SINGLE
  Can't parse single quoted string
YAML_PARSE_ERR_BAD_INLINE_IMPLICIT
  Can't parse inline implicit value '%s'
YAML_PARSE_ERR_BAD_IMPLICIT
  Unrecognized implicit value '%s'
YAML_PARSE_ERR_INDENTATION
  Error. Invalid indentation level
YAML_PARSE_ERR_INCONSISTENT_INDENTATION
  Inconsistent indentation level
YAML_LOAD_WARN_UNRESOLVED_ALIAS
  Can't resolve alias *%s
YAML_LOAD_WARN_NO_REGEXP_IN_REGEXP
  No 'REGEXP' element for Perl regexp
YAML_LOAD_WARN_BAD_REGEXP_ELEM
  Unknown element '%s' in Perl regexp
YAML_LOAD_WARN_GLOB_NAME
  No 'NAME' element for Perl glob
YAML_LOAD_WARN_PARSE_CODE
  Couldn't parse Perl code scalar: %s
YAML_LOAD_WARN_CODE_DEPARSE
  Won't parse Perl code unless $YAML::LoadCode is set
YAML_EMIT_ERR_BAD_LEVEL
  Internal Error: Bad level detected
YAML_PARSE_WARN_AMBIGUOUS_TAB
  Amibiguous tab converted to spaces
YAML_LOAD_WARN_BAD_GLOB_ELEM
  Unknown element '%s' in Perl glob
YAML_PARSE_ERR_ZERO_INDENT
  Can't use zero as an indentation width
YAML_LOAD_WARN_GLOB_IO
  Can't load an IO filehandle. Yet!!!
...
%line_adjust = map {($_, 1)}
  qw(YAML_PARSE_ERR_BAD_MAJOR_VERSION
     YAML_PARSE_WARN_BAD_MINOR_VERSION
     YAML_PARSE_ERR_TEXT_AFTER_INDICATOR
     YAML_PARSE_ERR_NO_ANCHOR
     YAML_PARSE_ERR_MANY_EXPLICIT
     YAML_PARSE_ERR_MANY_IMPLICIT
     YAML_PARSE_ERR_MANY_ANCHOR
     YAML_PARSE_ERR_ANCHOR_ALIAS
     YAML_PARSE_ERR_BAD_ALIAS
     YAML_PARSE_ERR_MANY_ALIAS
     YAML_LOAD_ERR_NO_CONVERT
     YAML_LOAD_ERR_NO_DEFAULT_VALUE
     YAML_LOAD_ERR_NON_EMPTY_STRING
     YAML_LOAD_ERR_BAD_MAP_TO_SEQ
     YAML_LOAD_ERR_BAD_STR_TO_INT
     YAML_LOAD_ERR_BAD_STR_TO_DATE
     YAML_LOAD_ERR_BAD_STR_TO_TIME
     YAML_LOAD_WARN_DUPLICATE_KEY
     YAML_PARSE_ERR_INLINE_MAP
     YAML_PARSE_ERR_INLINE_SEQUENCE
     YAML_PARSE_ERR_BAD_DOUBLE
     YAML_PARSE_ERR_BAD_SINGLE
     YAML_PARSE_ERR_BAD_INLINE_IMPLICIT
     YAML_PARSE_ERR_BAD_IMPLICIT
     YAML_LOAD_WARN_NO_REGEXP_IN_REGEXP
     YAML_LOAD_WARN_BAD_REGEXP_ELEM
     YAML_LOAD_WARN_REGEXP_CREATE
     YAML_LOAD_WARN_GLOB_NAME
     YAML_LOAD_WARN_PARSE_CODE
     YAML_LOAD_WARN_CODE_DEPARSE
     YAML_LOAD_WARN_BAD_GLOB_ELEM
     YAML_PARSE_ERR_ZERO_INDENT
    );
package YAML::Warning;
our @ISA = 'YAML::Error';
1;
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