Course of Raku / Essentials / Strings

Variable interpolation

Have you already noticed in the previous sections that sometimes the strings were quoted in single, but sometimes in double quotes? The difference is crucial.

Of course, you can use double quotes if you want to put a single quote inside the string with minimum effort:

say "O'Henry";

By the way, it is still better to use a proper apostrophe instead of a single quote as Raku is good at Unicode.

say 'O’Henry';

But the real power of double quotes is their ability to interpolate variables and—as we’ll see soon—to execute code! Examine the following program:

my $name = 'Karl';
say "Hello, $name!";

As you might expect, the program prints Hello, Karl!. The name of the $name variable (together with its sigil $) was replaced by the value of the variable.

The variable was interpolated with the value that the variable kept at the moment of interpolation, so if you change the content of $name and interpolate it again, the new value will be substituted. Let’s test it:

my $name = 'Karl';
say "Hello, $name!";

$name = 'Anna';
say "Hello, $name!";

The same string generates different messages this time:

Hello, Karl!
Hello, Anna!

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