Haifuckqueue, 59 bytes
{Hel}
$3{lo }
$3{W}
$1{o}
$1{rld}
$3{!}
$1!!!
!!!!!!!
!!!!!
Explanation:
{Hel} -- overwrite top 3 bytes as ascii of "Hel"
$3{lo } -- print top 3 items as characters and push ascii of "lo " to the stack
$3{W}
$1{o}
$1{rld}
$3{!}
$1!!! -- print top 1 item as character and th...
@emanresuA having played with this a tiny bit (I wrote it without really knowing whether/how it would work in practice), it's basically just {prefix notation OR postfix notation}; choose one and stick to it for the whole program or it'll instantly break