#!/usr/bin/perl

sub foo {
    $#_ = 3 if @_ > 3;  # limit to 4 args
    print "$_\n" for @_;
    print "---\n";
}

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

__END__
1
2
3
---
1
2
3
4
---
1
2
3
4
---