Sub::Util - A selection of utility subroutines for subs and CODE references
use Sub::Util qw( prototype set_prototype subname set_subname );
Sub::Util contains a selection of utility subroutines that are useful for
operating on subs and CODE references.
The rationale for inclusion in this module is that the function performs some
work for which an XS implementation is essential because it cannot be
implemented in Pure Perl, and which is sufficiently-widely used across CPAN
that its popularity warrants inclusion in a core module, which this is.
my $proto = prototype( $code )
Since version 1.40.
Returns the prototype of the given $code reference, if it has one, as a
string. This is the same as the CORE::prototype operator; it is included
here simply for symmetry and completeness with the other functions.
my $code = set_prototype $prototype, $code;
Since version 1.40.
Sets the prototype of the function given by the $code reference, or deletes
it if $prototype is undef. Returns the $code reference itself.
Caution: This function takes arguments in a different order to the previous
copy of the code from Scalar::Util. This is to match the order of
set_subname, and other potential additions in this file. This order has
been chosen as it allows a neat and simple chaining of other
Sub::Util::set_* functions as might become available, such as:
my $code =
set_subname name_here =>
set_prototype '&@' =>
set_attribute ':lvalue' =>
sub { ...... };
my $name = subname( $code )
Since version 1.40.
Returns the name of the given $code reference, if it has one. Normal named
subs will give a fully-qualified name consisting of the package and the
localname separated by ::. Anonymous code references will give __ANON__
as the localname. If the package the code was compiled in has been deleted
(e.g. using delete_package from Symbol), __ANON__ will be returned as
the package name. If a name has been set using set_subname, this name will be
returned instead.
This function was inspired by sub_fullname from the Sub::Identify manpage. The
remaining functions that Sub::Identify implements can easily be emulated
using regexp operations, such as
sub get_code_info { return (subname $_[0]) =~ m/^(.+)::(.*?)$/ }
sub sub_name { return (get_code_info $_[0])[0] }
sub stash_name { return (get_code_info $_[0])[1] }
Users of Sub::Name beware: This function is not the same as
Sub::Name::subname; it returns the existing name of the sub rather than
changing it. To set or change a name, see instead set_subname.
my $code = set_subname $name, $code;
Since version 1.40.
Sets the name of the function given by the $code reference. Returns the
$code reference itself. If the $name is unqualified, the package of the
caller is used to qualify it.
This is useful for applying names to anonymous CODE references so that stack
traces and similar situations, to give a useful name rather than having the
default of __ANON__. Note that this name is only used for this situation;
the set_subname will not install it into the symbol table; you will have to
do that yourself if required.
However, since the name is not used by perl except as the return value of
caller, for stack traces or similar, there is no actual requirement that
the name be syntactically valid as a perl function name. This could be used to
attach extra information that could be useful in debugging stack traces.
This function was copied from Sub::Name::subname and renamed to the naming
convention of this module.
The general structure of this module was written by Paul Evans
<leonerd@leonerd.org.uk>.
The XS implementation of set_subname was copied from the Sub::Name manpage by
Matthijs van Duin <xmath@cpan.org>
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