foo(1,2,3,4);

sub foo {
  my (@args) = @_; # now @args holds a _copy_ of all the arguments
}

##</code><code>##

sub foo {
  my $first = shift; # get the first argument and remove it from @_;
  my $last  = pop;   # get the last argument and remove it from @_;
}

##</code><code>##

my $i = 1;
inc($i);
sub inc {
  $i++;  #note: $i is not declared and read from @_
}

##</code><code>##

my $i = 1;
inc($i);
sub inc {
  my $i = shift;  # declare and read $i from @_
  $i++;
}