This seems like reason nr 128 in the series for passing args to subs as references to data structures rather than the structures themselves. In this case an arrayref.

Then you can use the high precedence (logical) Or, ||. Critically, this has higher precedence than =. So $dinner = $ham || $eggs; means dinner is ham or, if we've got no ham, eggs. As opposed to $dinner = $ham or get('takeaway'); which means dinner is ham, but if we fail to make dinner from ham, we're gonna send out.

As other monks remark, || forces scalar context on the LH operand, so if you pass a three-element array, you'd get '3'. But with an arrayref you're already in scalar context so you don't care.

The only disadvantage is, you don't use @_ explicitly. This is a disadvantage because that was what your question was about!

use strict;
use Data::Dumper;

my %lexicon = (
    foo => 'boink',
    bar => 'blink',
    baz => 'squirm',
);

sub
grop
{   
    my $lexlist = shift || [sort keys %lexicon];
    print Dumper($lexlist);
}
 
grop(['gump','snoop','grock']);
grop();
[download]

Which produces

$VAR1 = [
          'gump',
          'snoop',
          'grock'
        ];
$VAR1 = [
          'bar',
          'baz',
          'foo'
        ];
[download]

§ George Sherston