Course of Raku / Objects, I/O, and exceptions / Exceptions

Catching exceptions with try

When something goes wrong in a Raku program — a missing file, an explicit die — an exception is thrown. By default, an unhandled exception stops the program. The try block lets you run code that might fail without crashing.

You wrap the risky code in a try block. If an exception is thrown inside it, the block stops there, but the program continues:

my $result = try {
    die 'Boom!';
};

say "Still works";

The die is caught by the try, so the program does not crash — it carries straight on to the next statement and prints:

Still works

When the block fails like this, it evaluates to an undefined value, so $result is undefined:

say $result.defined; # False

The exception that was caught is stored in the special variable $!. You can read its message from there:

say $!.message; # Boom!

So try turns a fatal error into something your program can inspect and react to. If the block runs without any exception, $result holds its value, and $! is undefined.

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