I really doubt this prototype ($;$$) ever served a meaningful purpose...

But for the general case, you can always write a wrapper which calls the original

use v5.12.0;
use warnings;

package Somename;
use Data::Dumper;


foo(1,2,3,4,5);

sub foo($;$$) {

    my $one = shift;
    my $two = shift;
    my $three = shift;
    my $four = shift;
    my $five = shift;
    print Dumper [$four,$five];
}

package Othername;

# use Somename;

sub foo { &Somename::foo }  

foo(1..5);
[download]

Somename::foo() called too early to check prototype at d:/Perl/pm/foo_
+prototype.pl line 8.
$VAR1 = [
          4,
          5
        ];
$VAR1 = [
          4,
          5
        ];

Compilation finished at Sat Apr 15 00:12:57
[download]

Explanation for &Somename::foo

• the & helps ignoring the prototype
• the missing brackets mean it's called with the current @_
• the last position means it's return value is returned too.

NB: you can also define an Somename::import sub which automatically exports the foo you want into the callers namespace, whenever use Somename; is compiled.