man > Class::Struct

Che Dong

The user wants me to transform a Perl man page HTML document into an emoji-rich, visually scannable version. Let me carefully process this while following all the critical rules. Key rules to follow: 1. NEVER use

— start from

2. Section titles →

with ONE emoji prefix 3. Sub-sections →

with emoji prefix 4. Comments in code examples are NOT headings 5. ALL code MUST be wrapped in

...

6. Code blocks must contain EXACT original code — NO changes, NO emoji inside 7. Use standard

for ALL lists 8. Escape < and > as < and > 9. Output ONLY valid HTML 10. Preserve original HTML structure and section ordering 11. Add descriptive emoji 12. ALWAYS create a

🚀 Quick Reference

section as the second section 13. Condense to under 128,000 characters Let me identify the sections: - NAME - SYNOPSIS - DESCRIPTION (with sub-sections: The struct() function, Class Creation at Compile Time, Element Types and Accessor Methods, Initializing with "new") - EXAMPLES (with sub-sections: Example 1, Example 2, Example 3) - Author and Modification History Now let me structure the output: 1. Header/title (already exists, not a heading to add) 2. 🚀 Quick Reference (NEW - second section) 3. 📛 NAME 4. 📋 SYNOPSIS 5. 📖 DESCRIPTION - 🔧 The struct() function - 🏗️ Class Creation at Compile Time - 🏷️ Element Types and Accessor Methods - Scalar - Array - Hash - Class - 🎬 Initializing with "new" 6. 💡 EXAMPLES - Example 1 - Example 2 - Example 3 7. 📜 Author and Modification History I need to preserve the original links, but I also need to keep code blocks exact. The original has links inside code blocks for `Class::Struct` - I should NOT keep those inside code blocks per the rules. Wait, let me re-read rule 8: "Code blocks MUST contain EXACT original code — NO changes, NO added links, NO emoji inside

. NEVER put  inside a  block."

So I should remove the `` tags from inside code blocks. The original has them, but I should strip them out from code blocks. Actually wait - "NO changes" is contradictory with "NEVER put  inside". Let me interpret this as: don't add links, don't put links inside code blocks. The original has them, but for the code to be valid and copyable, I should strip them.

Actually, looking again - the rule says "Code blocks MUST contain EXACT original code — NO changes". But also "NEVER put  inside a  block". I think the intent is: the visible code (what gets copied) should be exact. So I should strip the  tags but keep the text content. This is what makes sense.

Let me also note that some code has comments using < and > or => which need to be preserved. In the SYNOPSIS, there's "package CLASS_NAME;" with all caps placeholders, but I should keep these as-is in code blocks.

Let me also handle list items. The Examples have bullet-style comment lines like "# user time used" - those should stay inside code blocks.

Wait, looking at Example 1 more carefully - the comments "# user time used", "# seconds", "# microseconds" are part of the code block. I need to keep them in the pre/code block.

Let me carefully construct the output now.

For the description sections, the text after the sub-headings has bullet-like descriptions (like "Scalar ('$' or '*$')" followed by a paragraph). These aren't really bullet points in the original — they're just paragraphs. I'll keep them as paragraphs.

Actually, looking at "Element Types and Accessor Methods" section, the descriptions for each type seem to be indented paragraphs (4-space indent). These could be lists but the original uses indented paragraphs. I'll keep them as is but use lists where appropriate.

Let me also note: the original has `` tags around things like "Perl Cookbook", "ELEMENT_LIST", "element", "name", "value" — these I should preserve.

Now let me draft the output:

For Quick Reference table:
- Use Case | Command | Description
- Declare array-based struct | use Class::Struct; struct( CLASS => [ name => '$' ]); | Create struct using array
- Declare hash-based struct | use Class::Struct; struct( CLASS => { name => '$' }); | Create struct using hash
- Compile-time declaration | use Class::Struct CLASS => [name => '$']; | Create class at compile time
- Create instance | $obj = MyClass->new; | Construct a new object
- Access scalar element | $obj->name | Get scalar value
- Set scalar element | $obj->name('value') | Assign scalar value
- Access array element | $obj->arr(2) | Get array element
- Set array element | $obj->arr(2, 'value') | Assign array element
- Initialize with new | MyClass->new(name => 'x') | Initialize elements at construction

Let me write this out now. I need to be careful with HTML escaping for < and > in code examples. Looking at the original code, I don't see raw < or > in the code (just =>, ->, @{}, $). Actually the $_[0] < 0 in Example 2 has  are literal text. Hmm, but rule 13 says: "ANY < or > NOT part of an allowed HTML tag... MUST be escaped as < and >". So even inside , raw < > should be escaped.

Let me check: yes, in  if I have `$_[0] < 0`, the ` [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
        # declare struct, based on hash:
struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
...
```

I'll preserve this structure - put the whole SYNOPSIS code section in one or more pre/code blocks. But it's pretty long. Let me break it into logical groups.

OK let me just write the final output now.

Class::Struct(3perl)              Perl Programmers Reference Guide              Class::Struct(3perl)

🚀 Quick Reference

🎯 Use Case 💻 Command 📝 Description
Declare array-based struct struct( CLASS => [ name => '$' ]) Faster, smaller struct backed by array
Declare hash-based struct struct( CLASS => { name => '$' }) More flexible struct backed by hash
Compile-time declaration use Class::Struct CLASS => [name => '$']; Create class at compile time
Create instance $obj = MyClass->new; Construct new struct object
Access scalar $val = $obj->name; Read scalar element
Set scalar $obj->name('value'); Assign scalar element
Access array element $obj->arr(2); Read array element by index
Set array element $obj->arr(2, 'v'); Assign array element by index
Initialize with new MyClass->new(name => 'x') Pass initial values at construction
Nested struct access $obj->inner->field Access field of nested struct


📛 NAME
Class::Struct - declare struct-like datatypes as Perl classes

📋 SYNOPSIS
use Class::Struct;
        # declare struct, based on array:
struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
        # declare struct, based on hash:
struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });

package CLASS_NAME;
use Class::Struct;
        # declare struct, based on array, implicit class name:
struct( ELEMENT_NAME => ELEMENT_TYPE, ... );

# Declare struct at compile time
use Class::Struct CLASS_NAME => [ELEMENT_NAME => ELEMENT_TYPE, ...];
use Class::Struct CLASS_NAME => {ELEMENT_NAME => ELEMENT_TYPE, ...};

# declare struct at compile time, based on array, implicit
# class name:
package CLASS_NAME;
use Class::Struct ELEMENT_NAME => ELEMENT_TYPE, ... ;

📦 Full example with all four element types:
package Myobj;
use Class::Struct;
        # declare struct with four types of elements:
struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );

$obj = new Myobj;               # constructor

                                # scalar type accessor:
$element_value = $obj->s;           # element value
$obj->s('new value');               # assign to element

                                # array type accessor:
$ary_ref = $obj->a;                 # reference to whole array
$ary_element_value = $obj->a(2);    # array element value
$obj->a(2, 'new value');            # assign to array element

                                # hash type accessor:
$hash_ref = $obj->h;                # reference to whole hash
$hash_element_value = $obj->h('x'); # hash element value
$obj->h('x', 'new value');          # assign to hash element

                                # class type accessor:
$element_value = $obj->c;           # object reference
$obj->c->method(...);               # call method of object
$obj->c(new My_Other_Class);        # assign a new object

📖 DESCRIPTION
🔍 Class::Struct exports a single function, struct. Given a list of element names and types, and optionally a class name, struct creates a Perl 5 class that implements a "struct-like" data structure.
🏗️ The new class is given a constructor method, new, for creating struct objects.
🎛️ Each element in the struct data has an accessor method, which is used to assign to the element and to fetch its value. The default accessor can be overridden by declaring a sub of the same name in the package. (See Example 2.)
🏷️ Each element's type can be scalar, array, hash, or class.

🔧 The struct() function
The struct function has three forms of parameter-list.
struct( CLASS_NAME => [ ELEMENT_LIST ]);
struct( CLASS_NAME => { ELEMENT_LIST });
struct( ELEMENT_LIST );
📌 The first and second forms explicitly identify the name of the class being created. The third form assumes the current package name as the class name.
⚡ An object of a class created by the first and third forms is based on an array, whereas an object of a class created by the second form is based on a hash. The array-based forms will be somewhat faster and smaller; the hash-based forms are more flexible.
🚫 The class created by struct must not be a subclass of another class other than UNIVERSAL.
🌱 It can, however, be used as a superclass for other classes. To facilitate this, the generated constructor method uses a two-argument blessing. Furthermore, if the class is hash-based, the key of each element is prefixed with the class name (see Perl Cookbook, Recipe 13.12).
⚠️ A function named new must not be explicitly defined in a class created by struct.
The ELEMENT_LIST has the form
NAME => TYPE, ...
📝 Each name-type pair declares one element of the struct. Each element name will be defined as an accessor method unless a method by that name is explicitly defined; in the latter case, a warning is issued if the warning flag (-w) is set.

🏗️ Class Creation at Compile Time
🕐 Class::Struct can create your class at compile time. The main reason for doing this is obvious, so your class acts like every other class in Perl. Creating your class at compile time will make the order of events similar to using any other class (or Perl module).
📊 There is no significant speed gain between compile time and run time class creation, there is just a new, more standard order of events.

🏷️ Element Types and Accessor Methods
The four element types — scalar, array, hash, and class — are represented by strings — '$', '@', '%', and a class name — optionally preceded by a '*'.
🎯 The accessor method provided by struct for an element depends on the declared type of the element.

🔢 Scalar ('$' or '*$')
The element is a scalar, and by default is initialized to undef (but see "Initializing with new").
✍️ The accessor's argument, if any, is assigned to the element.
🔁 If the element type is '$', the value of the element (after assignment) is returned. If the element type is '*$', a reference to the element is returned.

📚 Array ('@' or '*@')
The element is an array, initialized by default to ().
🔎 With no argument, the accessor returns a reference to the element's whole array (whether or not the element was specified as '@' or '*@').
🎯 With one or two arguments, the first argument is an index specifying one element of the array; the second argument, if present, is assigned to the array element. If the element type is '@', the accessor returns the array element value. If the element type is '*@', a reference to the array element is returned.
✨ As a special case, when the accessor is called with an array reference as the sole argument, this causes an assignment of the whole array element. The object reference is returned.

🗂️ Hash ('%' or '*%')
The element is a hash, initialized by default to ().
🔎 With no argument, the accessor returns a reference to the element's whole hash (whether or not the element was specified as '%' or '*%').
🔑 With one or two arguments, the first argument is a key specifying one element of the hash; the second argument, if present, is assigned to the hash element. If the element type is '%', the accessor returns the hash element value. If the element type is '*%', a reference to the hash element is returned.
✨ As a special case, when the accessor is called with a hash reference as the sole argument, this causes an assignment of the whole hash element. The object reference is returned.

🧬 Class ('Class_Name' or '*Class_Name')
🎯 The element's value must be a reference blessed to the named class or to one of its subclasses. The element is not initialized by default.
💥 The accessor's argument, if any, is assigned to the element. The accessor will croak if this is not an appropriate object reference.
🔁 If the element type does not start with a '*', the accessor returns the element value (after assignment). If the element type starts with a '*', a reference to the element itself is returned.

🎬 Initializing with new
🏭 struct always creates a constructor called new. That constructor may take a list of initializers for the various elements of the new struct.
📝 Each initializer is a pair of values: element name" => "value. The initializer value for a scalar element is just a scalar value. The initializer for an array element is an array reference. The initializer for a hash is a hash reference.
🧩 The initializer for a class element is an object of the corresponding class, or of one of it's subclasses, or a reference to a hash containing named arguments to be passed to the element's constructor.
👀 See Example 3 below for an example of initialization.

💡 EXAMPLES

📌 Example 1
🪆 Giving a struct element a class type that is also a struct is how structs are nested. Here, Timeval represents a time (seconds and microseconds), and Rusage has two elements, each of which is of type Timeval.
use Class::Struct;

struct( Rusage => {
    ru_utime => 'Timeval',  # user time used
    ru_stime => 'Timeval',  # system time used
});

struct( Timeval => [
    tv_secs  => '$',        # seconds
    tv_usecs => '$',        # microseconds
]);

# create an object:
my $t = Rusage->new(ru_utime=>Timeval->new(),
    ru_stime=>Timeval->new());

# $t->ru_utime and $t->ru_stime are objects of type Timeval.
# set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
$t->ru_utime->tv_secs(100);
$t->ru_utime->tv_usecs(0);
$t->ru_stime->tv_secs(5);
$t->ru_stime->tv_usecs(0);

📌 Example 2
🛡️ An accessor function can be redefined in order to provide additional checking of values, etc. Here, we want the count element always to be nonnegative, so we redefine the count accessor accordingly.
package MyObj;
use Class::Struct;

# declare the struct
struct ( 'MyObj', { count => '$', stuff => '%' } );

# override the default accessor method for 'count'
sub count {
    my $self = shift;
    if ( @_ ) {
        die 'count must be nonnegative' if $_[0] < 0;
        $self->{'MyObj::count'} = shift;
        warn "Too many args to count" if @_;
    }
    return $self->{'MyObj::count'};
}

package main;
$x = new MyObj;
print "\$x->count(5) = ", $x->count(5), "\n";
                        # prints '$x->count(5) = 5'

print "\$x->count = ", $x->count, "\n";
                        # prints '$x->count = 5'

print "\$x->count(-5) = ", $x->count(-5), "\n";
                        # dies due to negative argument!

📌 Example 3
🎬 The constructor of a generated class can be passed a list of element=>value pairs, with which to initialize the struct. If no initializer is specified for a particular element, its default initialization is performed instead. Initializers for non-existent elements are silently ignored.
🧩 Note that the initializer for a nested class may be specified as an object of that class, or as a reference to a hash of initializers that are passed on to the nested struct's constructor.
use Class::Struct;

struct Breed =>
{
    name  => '$',
    cross => '$',
};

struct Cat =>
[
    name     => '$',
    kittens  => '@',
    markings => '%',
    breed    => 'Breed',
];


my $cat = Cat->new( name => 'Socks',
           kittens  => ['Monica', 'Kenneth'],
           markings => { socks=>1, blaze=>"white" },
           breed    => Breed->new(name=>'short-hair', cross=>1),
      or:  breed    => {name=>'short-hair', cross=>1},
                );

print "Once a cat called ", $cat->name, "\n";
print "(which was a ", $cat->breed->name, ")\n";
print "had 2 kittens: ", join(' and ', @{$cat->kittens}), "\n";

📜 Author and Modification History
🛠️ Modified by Damian Conway, 2001-09-10, v0.62.

🔧 Modified implicit construction of nested objects.
✅ Now will also take an object ref instead of requiring a hash ref.
🆕 Also default initializes nested object attributes to undef, rather than calling object constructor without args
📋 Original over-helpfulness was fraught with problems:
    
        ⚠️ the class's constructor might not be called 'new'
        ⚠️ the class might not have a hash-like-arguments constructor
        ⚠️ the class might not have a no-argument constructor
        🔁 "recursive" data structures didn't work well:
            package Person;
struct { mother => 'Person', father => 'Person'};
        
    



🛠️ Modified by Casey West, 2000-11-08, v0.59.
➕ Added the ability for compile time class creation.

🛠️ Modified by Damian Conway, 1999-03-05, v0.58.

➕ Added handling of hash-like arg list to class ctor.
🔄 Changed to two-argument blessing in ctor to support derivation from created classes.
🔑 Added classname prefixes to keys in hash-based classes (refer to "Perl Cookbook", Recipe 13.12 for rationale).
🐛 Corrected behaviour of accessors for '*@' and '*%' struct elements. Package now implements documented behaviour when returning a reference to an entire hash or array element. Previously these were returned as a reference to a reference to the element.


🛠️ Renamed to Class::Struct and modified by Jim Miner, 1997-04-02.

❌ members() function removed.
📖 Documentation corrected and extended.
🚫 Use of struct() in a subclass prohibited.
✅ User definition of accessor allowed.
🔧 Treatment of '*' in element types corrected.
🔧 Treatment of classes as element types corrected.
✨ Class name to struct() made optional.
🔍 Diagnostic checks added.


🛠️ Originally Class::Template by Dean Roehrich.
# Template.pm   --- struct/member template builder
#   12mar95
#   Dean Roehrich
#
# changes/bugs fixed since 28nov94 version:
#  - podified
# changes/bugs fixed since 21nov94 version:
#  - Fixed examples.
# changes/bugs fixed since 02sep94 version:
#  - Moved to Class::Template.
# changes/bugs fixed since 20feb94 version:
#  - Updated to be a more proper module.
#  - Added "use strict".
#  - Bug in build_methods, was using @var when @$var needed.
#  - Now using my() rather than local().
#
# Uses perl5 classes to create nested data types.
# This is offered as one implementation of Tom Christiansen's
# "structs.pl" idea.


perl v5.34.0                                 2026-06-23                         Class::Struct(3perl)

man > Class::Struct

— start from

2. Section titles →

with ONE emoji prefix 3. Sub-sections →

🚀 Quick Reference

🚀 Quick Reference

📛 NAME

📋 SYNOPSIS

📖 DESCRIPTION

🔧 The `struct()` function

🏗️ Class Creation at Compile Time

🏷️ Element Types and Accessor Methods

🔢 Scalar ('$' or '*$')

📚 Array ('@' or '*@')

🗂️ Hash ('%' or '*%')

🧬 Class ('Class_Name' or '*Class_Name')

🎬 Initializing with `new`

💡 EXAMPLES

📌 Example 1

📌 Example 2

📌 Example 3

📜 Author and Modification History