What is @$ in perl?

Question

I came across this, expecting it to be a typo for $@:

use strict;
use warnings;

eval {
  my $error = Not::Here->new();
};

warn @$;

And to my surprise it outputs this:

Can't locate object method "new" via package "Not::Here" (perhaps you forgot to load "Not::Here"?) at dollar_array.pl line 6. ...caught at dollar_array.pl line 9.

I'm unable to find any information about @$, and it's not listed on perlvar, nor in eval

Since the output show caught at ..., it seems that this is something in the exception handling of perl.

Answer 1

@$ has no meaning (yet) in Perl. It exists because $$ exists (for each special variable "sigil-char", all other "another_sigil-char" variables exist). Therefore, warn gets no arguments - you can verify that by using just warn; - you'll get the same output.

Now, let's read the documentation for warn:

If the output is empty and $@ already contains a value (typically from a previous eval) that value is used after appending "\t...caught" to $@. This is useful for staying almost, but not entirely similar to die.

$@ contains the exception from the eval, so the behaviour is expected.