DB<105>  map { ( "x" => $_ ) } qw(1 2 3); 
 => ("x", 1, "x", 2, "x", 3)

  DB<106>  map { ( "x" => $y ) } qw(1 2 3); 
 => ("x", undef, "x", undef, "x", undef)

  DB<110> @opts = map { ( "$_=s" => \$opt{$_} ) } @vals;
 => ("title=s", \undef, "artist=s", \undef, "album=s", \undef)