Algol 68 allows spaces in identifiers. That means one has to use one of the &quot;stropping&quot; techniques to distinguish keywords from identifiers--case stropping (IF p THEN foo ELSE bar FI), quote stropping a la the old IBM Algol F Algol 60 compiler (&#x27;if&#x27; p &#x27;then&#x27; foo &#x27;else&#x27; bar &#x27;fi&#x27;), and at least one other I don&#x27;t remember offhand.