use Data::Dumper qw(Dumper);

$SIG{__WARN__} = sub { &handle_it(@_); warn @_ };
$SIG{__DIE__}  = sub { &handle_it(@_);  die @_ };

sub handle_it {
  print Dumper \@_;
}

##</code><code>##

die "foo";    # prints as "foo at script line whatever\n" - stringified
#die "foo", "foo";  # stringified - same as above but with "foofoo"
#die {hi => 'there'};  # not stringified - shows correctly as a hashref
#die 'foo',{hi => 'there'}; # stringified "fooHASH{whatever}"
#warn {hi => 'there'};  # always stringified

##</code><code>##

die "Something happend", {extra_argument_to_show_pretty_error => 1};