Using ampersands and parens when calling a Perl sub

#!/usr/bin/perl

sub t {
  print "in t\n";
  print "@_\n";
  &s;
}

sub s {
  print "in s\n";
  print "@_\n";
}

t(1,2);
print "out\n";
print "@_\n";

Output:

in t
1 2
in s
1 2
out

As you see,&s output 1 2 when no parameter is passed. Is this a feature or a bug?

Tested version is 5.8.8.