#!/usr/bin/perl
use strict;
use warnings;

{   package OnlyAString;
    use overload fallback=>0, '""'=>sub { ${shift()} }
}
{   package ICanStringify;
    use overload fallback=>undef, '0+'=>sub { ${shift()} }
}
{   package OnlyANumber;
    use overload fallback=>0, '0+'=>sub { ${shift()} }
}

bless my $s1=\do {my $x=111}, 'OnlyAString';
bless my $s2=\do {my $x=222}, 'ICanStringify';
bless my $s3=\do {my $x=333}, 'OnlyANumber';
can_str($s1);
can_str($s2);
can_str($s3);

use overload ();
sub can_str {
    my $s = shift;
    print "Object ", overload::StrVal($s), ":\n";
    print "    \"\" ", overload::Method($s,'""')
        ?"IS":"is NOT", " overloaded\n";
    my $e = eval { "$s" };
    print "    stringification ", defined($e)
        ?"WORKED: $e\n":"DIDN'T work: $@\n";
}