\subsection{Expressions}
Patterns in \gls{CLEAN} can be used as predicates as well \citep[\citesection{3.4.3}]{plasmeijer_clean_2021}.
Using the \cleaninline{=:} operator, a value is tested against a pattern.
-Variable names are not allowed but wildcard patterns \cleaninline{\_} are.
+Variable names are not allowed but wildcard patterns (\cleaninline{\_}) are.
\begin{lstClean}[label={lst:matches_pattern_expression},caption={Examples of \emph{matches pattern} expressions.}]
isNil :: [a] -> Bool