Hello everyone,

I seek your wisdom on this question: Is there a way to ask Perl whether an object supports stringification, including via "magic autogeneration"? The only way I've found so far was by trying to eval the stringification, like in the code below. The specific case here is the "ICanStringify" class, where overload::Method($s,'""') is false, but the object still stringifies. Did I miss some function somewhere that can tell me whether that class will stringify?

#!/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";
}
[download]

Output:

Object OnlyAString=SCALAR(0x3684370):
    "" IS overloaded
    stringification WORKED: 111
Object ICanStringify=SCALAR(0x3664210):
    "" is NOT overloaded
    stringification WORKED: 222
Object OnlyANumber=SCALAR(0x3679682):
    "" is NOT overloaded
    stringification DIDN'T work: Operation """": no method found, argu
+ment in overloaded package OnlyANumber at test.pl line 28.
[download]

The background is that I have a function that accepts only strings. Because passing a reference was a mistake I made a few times, I started warning if any references were passed to it, including objects. But then I realized that some objects stringify and that's useful, and that some objects die when you try to stringify them. I'd like to loosen the restrictions, and still warn on references and objects that don't stringify, but not on objects that stringify.

Any wisdom on this topic would be greatly appreciated!

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