Scalar::Properties 0.12

Scalar::Properties is a Perl module package that contains run-time properties on scalar variables.

SYNOPSIS

use Scalar::Properties;
my $val = 0->true;
if ($val && $val == 0) {
print "yup, its true alright...n";
}

my @text = (
hello world->greeting(1),
forget it,
hi there->greeting(1),
);
print grep { $_->is_greeting } @text;

my $l = hello world->length;

Scalar::Properties attempts to make Perl more object-oriented by taking an idea from Ruby: Everything you manipulate is an object, and the results of those manipulations are objects themselves.

hello world->length
(-1234)->abs
"oh my god, its full of properties"->index(g)

The first example asks a string to calculate its length. The second example asks a number to calculate its absolute value. And the third example asks a string to find the index of the letter g.

Using this module you can have run-time properties on initialized scalar variables and literal values. The word properties is used in the Perl 6 sense: out-of-band data, little sticky notes that are attached to the value. While attributes (as in Perl 5s attribute pragma, and see the Attribute::* family of modules) are handled at compile-time, properties are handled at run-time.
Internally properties are implemented by making their values into objects with overloaded operators. The actual properties are then simply hash entries.
Most properties are simply notes you attach to the value, but some may have deeper meaning. For example, the true and false properties plays a role in boolean context, as the first example of the Synopsis shows.

Properties can also be propagated between values. For details, see the EXPORTS section below. Here is an example why this might be desirable:

pass_on(approximate);
my $pi = 3->approximate(1);
my $circ = 2 * $rad * $pi;

# now $circ->approximate indicates that this value was derived
# from approximate values

Please dont use properties whose name start with an underscore; these are reserved for internal use.

You can set and query properties like this:

$var->myprop(1)

sets the property to a true value.

$var->myprop(0)

sets the property to a false value. Note that this doesnt delete the property (to do so, use the del_props method described below).

$var->is_myprop, $var->has_myprop

returns a true value if the property is set (i.e., defined and has a true value). The two alternate interfaces are provided to make querying attributes sound more natural. For example:

$foo->is_approximate;
$bar->has_history;