Perl - messing try/catch with eval

Question

How to catch exception from inner eval {}?

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

use Try::Tiny;
use Exception::Class ('T');

use Data::Dumper;

try {
    eval {
        T->throw("Oops");
    };
    } catch {
        print Dumper \$_;
    };
}

We have got not Exception::Class submodule, but scalar instead. More precisely, I have a lot of legacy code with require, and require seems to use eval inside.

Answer 1

You can automatically upconvert exceptions as follows:

#!/usr/bin/perl
use strict;
use warnings;
use feature qw( say );

use Try::Tiny;
use Exception::Class ('T');

$SIG{__DIE__} = sub {
   die($_[0]) if !defined($^S);
   die($_[0]) if ref($_[0]) eq 'T';
   T->throw($_[0]);
};

try {
    die "foo";
} catch {
    say ref($_) || "Not reference";
    print $_;
};

try {
    T->throw("foo");
} catch {
    say ref($_) || "Not reference";
    say $_;
};

Answer 2

If an exception is encountered inside an eval block, the return value of the block is undef (or an empty list in list context) and Perl sets the special variable $@ with the error message. The error message is usually a simple scalar but it can be a reference or blessed reference -- one way that it gets set is with the argument to a die call, and any type of value may be passed to that function.

try {
    eval {
        T->throw("Oops"); 1;
    } or do {
        warn "Exception caught in eval: $@";
        # rethrow the exception outside eval
        if (ref($@) eq 'T') {
            $@->rethrow;
        } else {
            T->throw("Oops: $@");
        }
    }
} catch {
    print Dumper \$_;
};