Macro Hep

Trying to create a DK macro that casts Howling Blast normally, Death Strike when holding shift, and casts Rune Strike whenever able to

will the following work?

#showtooltip
/cast [nomod] Howling Blast;
/cast [nomod] !Rune Strike;
/cast [mod:shift] Death Strike;
/cast [mod:shift] !Rune Strike;
/run UIErrorsFrame:Clear()

I know there's probably a more efficient way to write it, but will this work? I'm not sure on the semicolons and whether the repeat of [nomod] and [mod:shift] from !Rune strike will work or if it has to be a cast sequence or what.

Somewhat new to macros so any help would be appreciated!