PropertyList is a generic ordered list with O(1) lookup by key (id or custom index key). It supports case-insensitive indexing, multi-value entries, disabled items, and serialization with pluralization handling. This pattern is reusable for any scenario requiring a typed, indexed list with CRUD operations and JSON export.

MutationTracker records set/unset operations on objects and can compact and replay them. It is used by VariableScope to track environment changes. This is a clean, self-contained pattern for implementing undo/redo or change propagation in data models.

SuperString provides a Substitutor class that resolves {{variable}} placeholders using a VariableList or plain object. It supports recursive resolution, poly-chain lookups (parent scopes), and dynamic variables (e.g., $guid, $timestamp). The engine is efficient and handles edge cases like escaped braces. This could be extracted as a standalone template engine.

UrlMatchPattern implements Google Chrome's match pattern syntax (e.g., <all_urls>, http://*/*) for URL matching. It parses patterns into scheme, host, path components and provides a test() method. This is a self-contained, well-tested module reusable for any URL filtering or proxy configuration logic.

The content-info module analyzes HTTP response headers and body to determine MIME type, file extension, and filename (from Content-Disposition). It handles RFC 5987 encoded filenames, quoted pairs, and multiple file extensions. This is a standalone utility that could be reused in any HTTP client or file download tool.