Why I can't omit the () here?

Question

SaveImages @img_sources;

The above will report:

Array found where operator expected 

Why can't I omit the () here?

Answer 1

because your SaveImages subroutine is declared after the call. Parentheses are not necessary if a subroutine is declared before the call.

example:

use strict;
use warnings;
use Data::Dumper;
my @ar = (1, 2);
fn @ar;
sub fn
{
    print Dumper \@_;
}

does not work, while

use strict;
use warnings;
use Data::Dumper;
my @ar = (1, 2);
sub fn
{
    print Dumper \@_;
}
fn @ar;

works.

This is an expected behavior and is pointed out in the camel book.