use overload. Here is a class that returns "foo" in a string context, and retutns 1 in numeric context.

package SampleOverload;

use overload '""' => \&as_string;
use overload '0+' => \&as_num;

sub new {
    bless { str => "foo", num => 1 }, shift;
}

sub as_string {
    shift()->{str};
}

sub as_num {
    shift()->{num};
}
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Interesting examples of modules using overload is y2k and Dunce::time, that magically fixes y2k or 10-digit time problem.

--
Tatsuhiko Miyagawa
miyagawa@cpan.org