Course of Raku / Advanced / More about built-in types / Quoting constructs 🆕

Quoting adverbs

The behaviour of a quoting construct can be tuned with adverbs. Each quoting feature — interpolating scalars, running embedded closures, processing backslashes — is controlled by its own adverb, which switches that one feature on or off, so you can start from q or Q and add back exactly the features you need.

Some common adverbs:

• :s / :scalar — interpolate scalar variables ($x)
• :c / :closure — interpolate embedded code in { … }
• :b / :backslash — process backslash escapes like \n

Add one to q to enable a single feature. For example, allow embedded code but nothing else:

say q/result: {3 * 4}/;   # result: {3 * 4}  — plain q leaves the block untouched
say q:c/result: {3 * 4}/; # result: 12        — :c runs the block

With plain q the { 3 * 4 } is printed verbatim; only :c makes the block run and inserts its value, while a $variable would still be left alone. Note the /…/ delimiters here: delimiting the string with {…} would still parse — the compiler counts the nested braces correctly — but then the inner { 3 * 4 } is read as part of the delimited text rather than as a closure, so :c would leave it literal. Whenever the text contains a { … } block, pick a delimiter other than {…} so the closure actually runs. You can add scalar interpolation to the otherwise-literal Q:

my $name = 'Anna';
say Q:s{Hi, $name}; # Hi, Anna

Adverbs also turn features off with a !. To use qq but keep $ literal:

my $price = 5;
say qq:!s{costs $price dollars}; # costs $price dollars

qq is equivalent to Q with all the interpolation adverbs switched on, and q is equivalent to Q with a smaller set. The adverbs give you fine-grained control between those two extremes.

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