GV Functions A GV is a structure which corresponds to to a Perl typeglob, ie *foo. It is a structure that holds a pointer to a scalar, an array, a hash etc, corresponding to $foo, @foo, %foo.

GVs are usually found as values in stashes (symbol table hashes) where Perl stores its global variables.

If gv is a typeglob whose subroutine entry is a constant sub eligible for inlining, or gv is a placeholder reference that would be promoted to such a typeglob, then returns the value returned by the sub. Otherwise, returns NULL.

Converts a scalar into a typeglob. This is an incoercible typeglob; assigning a reference to it will assign to one of its slots, instead of overwriting it as happens with typeglobs created by SvSetSV. Converting any scalar that is SvOK() may produce unpredictable results and is reserved for perl's internal use.

gv is the scalar to be converted.

stash is the parent stash/package, if any.

name and len give the name. The name must be unqualified; that is, it must not include the package name. If gv is a stash element, it is the caller's responsibility to ensure that the name passed to this function matches the name of the element. If it does not match, perl's internal bookkeeping will get out of sync.

flags can be set to SVf_UTF8 if name is a UTF-8 string, or the return value of SvUTF8(sv). It can also take the GV_ADDMULTI flag, which means to pretend that the GV has been seen before (i.e., suppress "Used once" warnings).

The old form of gv_init_pvn(). It does not work with UTF-8 strings, as it has no flags parameter. If the multi parameter is set, the GV_ADDMULTI flag will be passed to gv_init_pvn().

Same as gv_init_pvn(), but takes a nul-terminated string for the name instead of separate char * and length parameters.

Same as gv_init_pvn(), but takes an SV * for the name instead of separate char * and length parameters. flags is currently unused.

Like "gv_fetchmeth_pvn", but lacks a flags parameter.

Exactly like "gv_fetchmeth_pvn", but takes the name string in the form of an SV instead of a string/length pair.

Exactly like "gv_fetchmeth_pvn", but takes a nul-terminated string instead of a string/length pair.

Returns the glob with the given name and a defined subroutine or NULL. The glob lives in the given stash, or in the stashes accessible via @ISA and UNIVERSAL::.

The argument level should be either 0 or -1. If level==0, as a side-effect creates a glob with the given name in the given stash which in the case of success contains an alias for the subroutine, and sets up caching info for this glob.

The only significant values for flags are GV_SUPER and SVf_UTF8.

GV_SUPER indicates that we want to look up the method in the superclasses of the stash.

The GV returned from gv_fetchmeth may be a method cache entry, which is not visible to Perl code. So when calling call_sv, you should not use the GV directly; instead, you should use the method's CV, which can be obtained from the GV with the GvCV macro.

This is the old form of "gv_fetchmeth_pvn_autoload", which has no flags parameter.

Exactly like "gv_fetchmeth_pvn_autoload", but takes the name string in the form of an SV instead of a string/length pair.

Exactly like "gv_fetchmeth_pvn_autoload", but takes a nul-terminated string instead of a string/length pair.

Same as gv_fetchmeth_pvn(), but looks for autoloaded subroutines too. Returns a glob for the subroutine.

For an autoloaded subroutine without a GV, will create a GV even if level < 0. For an autoloaded subroutine without a stub, GvCV() of the result may be zero.

Currently, the only significant value for flags is SVf_UTF8.

Returns the glob which contains the subroutine to call to invoke the method on the stash. In fact in the presence of autoloading this may be the glob for "AUTOLOAD". In this case the corresponding variable $AUTOLOAD is already setup.

The third parameter of gv_fetchmethod_autoload determines whether AUTOLOAD lookup is performed if the given method is not present: non-zero means yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling gv_fetchmethod is equivalent to calling gv_fetchmethod_autoload with a non-zero autoload parameter.

These functions grant "SUPER" token as a prefix of the method name. Note that if you want to keep the returned glob for a long time, you need to check for it being "AUTOLOAD", since at the later time the call may load a different subroutine due to $AUTOLOAD changing its value. Use the glob created as a side effect to do this.

These functions have the same side-effects as gv_fetchmeth with level==0. The warning against passing the GV returned by gv_fetchmeth to call_sv applies equally to these functions.

Returns a pointer to the stash for a specified package. Uses strlen to determine the length of name, then calls gv_stashpvn().

Returns a pointer to the stash for a specified package. The namelen parameter indicates the length of the name, in bytes. flags is passed to gv_fetchpvn_flags(), so if set to GV_ADD then the package will be created if it does not already exist. If the package does not exist and flags is 0 (or any other setting that does not create packages) then NULL is returned.

Flags may be one of:

    GV_ADD
    SVf_UTF8
    GV_NOADD_NOINIT
    GV_NOINIT
    GV_NOEXPAND
    GV_ADDMG

The most important of which are probably GV_ADD and SVf_UTF8.

Note, use of gv_stashsv instead of gv_stashpvn where possible is strongly recommended for performance reasons.

Returns a pointer to the stash for a specified package. See "gv_stashpvn".

Note this interface is strongly preferred over gv_stashpvn for performance reasons.

If the typeglob gv can be expressed more succinctly, by having something other than a real GV in its place in the stash, replace it with the optimised form. Basic requirements for this are that gv is a real typeglob, is sufficiently ordinary, and is only referenced from its package. This function is meant to be used when a GV has been looked up in part to see what was there, causing upgrading, but based on what was found it turns out that the real GV isn't required after all.

If gv is a completely empty typeglob, it is deleted from the stash.

If gv is a typeglob containing only a sufficiently-ordinary constant sub, the typeglob is replaced with a scalar-reference placeholder that more compactly represents the same thing.

cpanm less

perl -MCPAN -e shell
install less