WARNING: Always be careful when making changes to the registry. If vital system information gets changed by mistake, your system could become inoperable. Always make certain you have a backup of your registry before you start making modifications.

The Registry module automatically creates objects for the top-level registry trees. These objects are created in the main:: namespace, and each key that you open or create is accessed via one of these root objects. The top-level objects are:

$HKEY_CLASSES_ROOT
$HKEY_CURRENT_USER
$HKEY_LOCAL_MACHINE
$HKEY_USERS
$HKEY_PERFORMANCE_DATA
$HKEY_CURRENT_CONFIG
$HKEY_DYN_DATA

If you are outside of the main (default) namespace, you should package declare the keys, e.g., $main::HKEY_USERS.

use Win32::Registry;
$p = "SOFTWARE\Microsoft\Windows NT\CurrentVersion";
$HKEY_LOCAL_MACHINE->Open($p, $CurrVer) || die "Open $!";

This example creates a key object $CurrVer for the CurrentVersion key for Windows NT. This key contains several values for the current version of the operating system. With the new key open, you can read or change the values it contains (every key has at least one unnamed, default value), or open and create subkeys. The Open method can create key objects only for existing keys.

Registry values are represented in Win32::Registry functions by three elements: the name of the value, the data type of the value, and the value itself. There are several different data types for the values. Win32::Registry defines the following constants for these types:

REG_SZ

String data

REG_DWORD

Unsigned four-byte integer

REG_MULTI_SZ

Multiple strings delimited with NULL

REG_EXPAND_SZ

Strings that expand (e.g., based on environment variables)

REG_BINARY

Binary data (no particular format is assumed)