sub unpack_named_first {
  my ($pos1,  $pos2 ,%arg) = @_;        # unpack 
  my ($name1, $name2)      = @arg{'name1','name2'} 
 
  $pos1       // die("Missing arg!");   # obligatory
  $pos2       //= 42;                   # default
  $name1      // die("Missing arg!");   # obligatory
  #$name2                               # optional
 
  # ...etc
}