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Programs that must fail #9

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Rakudo 2026.08 rejects this broken program; Raku++ 5.0.0-g312cde8e runs it anyway

The program is broken on purpose, so the right behaviour is a compile-time error. Rakudo 2026.08 reports one; Raku++ 5.0.0-g312cde8e accepts the program without an error. Here the reference compiler is right. This difference is preserved as a Rakumap finding ↗

The program

my $value = :;

Run executes the program in your browser, with the Raku++ build this site ships. Edit it and try variations.

What each compiler printed

Rakudo 2026.08

(printed nothing)

Raku++ 5.0.0-g312cde8e

(printed nothing)

Error messages

Rakudo 2026.08

===SORRY!=== Error while compiling invalid-00000048.raku
Malformed initializer
at invalid-00000048.raku:1
------> my $value = :<HERE>;
    expecting any of:
        colon pair

Raku++ 5.0.0-g312cde8e

(no error — the program ran to the end)

invalid-v1 · seed 48 · recorded 2026-09-29 with Rakudo 2026.08 and Raku++ 5.0.0-g312cde8e · Source on GitHub ↗