String (or text) constant values must use double or single quotes, as indicated in the example here:
%%[ var @statusTier set @statusTier = "Gold" ]%%
If quotation marks appear within the text, string constants can escape the delimiting quote when their quote type is switched (to single or double). Alternative quote characters, such as smart quotes, are not supported.
%%[ var @bonusProduct set @bonusProduct = 'Our "Uber" Umbrella' ]%%