Syntax...:Assert(3pm)

💖 Syntax...:Assert(3pm) 💖

okay bestie, so this is the manual page for Syntax::Keyword::Assert — a User Contributed Perl Documentation joint, and honestly? it's giving zero runtime cost and we're obsessed. 💅

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✨ NAME ✨

Syntax::Keyword::Assert — it's an assert keyword for Perl, and the whole point is that it costs you literally nothing at runtime. no cap. 🫶

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🌸 SYNOPSIS 🌸

use Syntax::Keyword::Assert;

my $obj = bless {}, "Foo";
assert($obj isa "Bar");
# => Assertion failed (Foo=HASH(0x11e022818) isa "Bar")

assert($x > 0, "x must be positive");
# => x must be positive

like look at that error message. it's so helpful. it tells you the actual expression that flopped. iconic behaviour fr fr. 😭

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🦋 DESCRIPTION 🦋

okay so Syntax::Keyword::Assert is a syntax extension for Perl, and what it does is add an assert keyword into your life. that's it. that's the vibe. ✨

By default, assertions are enabled. but — plot twist — you can turn them off by setting $ENV{PERL_ASSERT_ENABLED} to false before this module gets loaded:

BEGIN { $ENV{PERL_ASSERT_ENABLED} = 0 }  # Disable assertions

⚠️ note the before it's loaded part, bestie. the BEGIN block is doing the heavy lifting here. don't come crying to me if you set it after. 🙈

When assertions are disabled, the assert are completely ignored at compile phase, which results in zero runtime cost. that's the moment. 🌈

This is what makes Syntax::Keyword::Assert ideal for use in production environments — because it does not introduce any performance penalties when assertions are not needed. your prod boxes stay fast, your dev boxes stay loud. main character energy. 👑

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👑 KEYWORDS 👑

💜 assert

assert(EXPR)
assert(EXPR, MESSAGE)

If EXPR is truthy in scalar context, then happens nothing. like, literally nothing. silence. tranquility. 🧘

Otherwise? it dies with a user-friendly error message. 💀 (politely, though. user-friendly, remember.)

Here are some examples:

assert("apple" eq "banana");  # => Assertion failed ("apple" eq "banana")
assert(123 != 123);           # => Assertion failed (123 != 123)
assert(1 > 10);               # => Assertion failed (1 > 10)

You can also hand it a custom error message as the second argument:

assert($x > 0, "x must be positive");
# => x must be positive

now here's the good part — the message expression is lazily evaluated. it only gets evaluated when the assertion fails. so it's equivalent to:

$cond || do { die $msg }

which means you can go absolutely feral and put expensive computations or side effects in that message without worrying about performance when the assertion passes:

assert($x > 0, expensive_debug_info());
# expensive_debug_info() is NOT called if $x > 0

NOT called. bestie. that's the whole flex. 🔥

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🎀 SEE ALSO 🎀

• PerlX::Assert — this one also uses a keyword plugin, but it depends on Keyword::Simple. and its error message does not include the failed expression. (so you don't get the receipts. tragic.) 😔
• Devel::Assert — gives you similar functionality, but it does not use a keyword plugin.

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💖 LICENSE 💖

Copyright (C) kobaken.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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🌟 AUTHOR 🌟

kobaken <kentafly88@gmail.com>

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and that's the whole page, bestie!! go assert something. responsibly. 💅

mwah 💋 — this was perl v5.42.3, dated 2026-08-20, and you just read Syntax...:Assert(3pm). slay. 🌸✨