$\="\n";
$_='Hello World!'; print;
$_=pack'(U)*',map{hex}unpack'(H5)*'; print;
$_=pack'(H5)*',map{sprintf"%05X",$_}unpack'(U)*'; print;

##</code><code>##

$\="\n";
$_='Hello World!'; print;
$_=pack'(U)*',map{hex}unpack'(H4)*'; print;
$_=pack'(H4)*',map{sprintf"%04X",$_}unpack'(U)*'; print;

##</code><code>##

$\="\n";
$_='Hello World!'; print;
$_=pack'(U)*',map{hex}unpack'(H4)*'; print;
$_=pack'n*',unpack'(U)*'; print