map, or indicate the module, like List.map, or type signatures, like int -> float.^ and $ to indicate where the matched string should start or end, respectively.| Arg | Parsing of command line arguments. | 
| Arg_helper | Decipher command line arguments of the form
        <value> | <key>=<value> | 
| Array | Array operations. | 
| ArrayLabels | Array operations. | 
| Ast_helper | Helpers to produce Parsetree fragments | 
| Ast_invariants | Check AST invariants | 
| Ast_iterator | 
 | 
| Ast_mapper | The interface of a -ppx rewriter | 
| Asttypes | Auxiliary AST types used by parsetree and typedtree. | 
| Attr_helper | Helpers for attributes | 
| Bigarray | Large, multi-dimensional, numerical arrays. | 
| Buffer | Extensible buffers. | 
| Build_path_prefix_map | |
| Builtin_attributes | |
| Bytes | Byte sequence operations. | 
| BytesLabels | Byte sequence operations. | 
| Callback | Registering OCaml values with the C runtime. | 
| CamlinternalFormat | |
| CamlinternalFormatBasics | |
| CamlinternalLazy | Run-time support for lazy values. | 
| CamlinternalMod | Run-time support for recursive modules. | 
| CamlinternalOO | Run-time support for objects and classes. | 
| Ccomp | |
| Char | Character operations. | 
| Clflags | Command line flags | 
| Complex | Complex numbers. | 
| Condition | Condition variables to synchronize between threads. | 
| Config | |
| Consistbl | |
| Depend | Module dependencies. | 
| Digest | MD5 message digest. | 
| Docstrings | Documentation comments | 
| Dynlink | Dynamic loading of object files. | 
| Ephemeron | Ephemerons and weak hash table | 
| Event | First-class synchronous communication. | 
| Filename | Operations on file names. | 
| Float | Floating-point arithmetic | 
| Format | Pretty-printing. | 
| Gc | Memory management control and statistics; finalised values. | 
| Genlex | A generic lexical analyzer. | 
| Graphics | Machine-independent graphics primitives. | 
| GraphicsX11 | Additional graphics primitives for the X Windows system. | 
| Hashtbl | Hash tables and hash functions. | 
| Identifiable | Uniform interface for common data structures over various things. | 
| Int32 | 32-bit integers. | 
| Int64 | 64-bit integers. | 
| Lazy | Deferred computations. | 
| Lexer | |
| Lexing | The run-time library for lexers generated by  | 
| List | List operations. | 
| ListLabels | List operations. | 
| Location | Source code locations (ranges of positions), used in parsetree. | 
| Longident | Long identifiers, used in parsetree. | 
| Map | Association tables over ordered types. | 
| Marshal | Marshaling of data structures. | 
| Misc | |
| MoreLabels | Extra labeled libraries. | 
| Mutex | Locks for mutual exclusion. | 
| Nativeint | Processor-native integers. | 
| Numbers | Modules about numbers, some of which satisfy  | 
| Obj | Operations on internal representations of values. | 
| Oo | Operations on objects | 
| Parse | Entry points in the parser | 
| Parser | |
| Parsetree | Abstract syntax tree produced by parsing | 
| Parsing | The run-time library for parsers generated by  | 
| Pervasives | Pervasive operations. | 
| Pparse | Driver for the parser, external preprocessors and ast plugin hooks | 
| Pprintast | |
| Printast | |
| Printexc | Facilities for printing exceptions and inspecting current call stack. | 
| Printf | Formatted output functions. | 
| Profile | Compiler performance recording | 
| Queue | First-in first-out queues. | 
| Random | Pseudo-random number generators (PRNG). | 
| Scanf | Formatted input functions. | 
| Seq | Functional Iterators | 
| Set | Sets over ordered types. | 
| Simplif | Lambda simplification and lambda plugin hooks | 
| Sort | Sorting and merging lists. | 
| Spacetime | Profiling of a program's space behaviour over time. | 
| Stack | Last-in first-out stacks. | 
| StdLabels | Standard labeled libraries. | 
| Str | Regular expressions and high-level string processing | 
| Stream | Streams and parsers. | 
| String | String operations. | 
| StringLabels | String operations. | 
| Strongly_connected_components | Kosaraju's algorithm for strongly connected components. | 
| Syntaxerr | Auxiliary type for reporting syntax errors | 
| Sys | System interface. | 
| Targetint | Target processor-native integers. | 
| Tbl | |
| Terminfo | |
| Thread | Lightweight threads. | 
| ThreadUnix | Thread-compatible system calls. | 
| Typemod | Type-checking of the module language and typed ast plugin hooks | 
| Uchar | Unicode characters. | 
| Unix | Interface to the Unix system. | 
| UnixLabels | Interface to the Unix system. | 
| Warnings | |
| Weak | Arrays of weak pointers and hash sets of weak pointers. |