Scalar::Util - A selection of general-utility scalar subroutines
use Scalar::Util qw(blessed dualvar reftype weaken isweak);
Scalar::Util contains a selection of subroutines that people have expressed would be nice to have in the perl core, but the usage would not really be high enough to warrant the use of a keyword, and the size so small such that being individual extensions would be wasteful.
Scalar::Util does not export any subroutines. The subroutines defined are
If EXPR evaluates to a blessed reference the name of the package that it is blessed into is returned. Otherwise
undef is returned.
Returns a scalar that has the value NUM in a numeric context and the value STRING in a string context.
$foo = dualvar 10, "Hello"; $num = $foo + 2; # 12 $str = $foo . " world"; # Hello world
If EXPR is a scalar which is a weak reference the result is true.
Returns true if SCALAR is readonly.
If EXPR evaluates to a reference the type of the variable referenced is returned. Otherwise
undef is returned.
Return true if the result of EXPR is tainted
REF will be turned into a weak reference. This means that it will not hold a reference count on the object it references. Also when the reference count on that object reaches zero, REF will be set to undef.
This is useful for keeping copies of references , but you don't want to prevent the object being DESTROY-ed at its usual time.
Copyright (c) 1997-2000 Graham Barr <firstname.lastname@example.org>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
except weaken and isweak which are
Copyright (c) 1999 Tuomas J. Lukka <email@example.com>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as perl itself.
The weaken and isweak subroutines in this module and the patch to the core Perl were written in connection with the APress book `Tuomas J. Lukka's Definitive Guide to Object-Oriented Programming in Perl', to avoid explaining why certain things would have to be done in cumbersome ways.