Add custom error message support

[kfly8]

Problem

When an assertion fails, the default error message (e.g., Assertion failed (0 == 1)) may not clearly explain what went wrong.

Solution

Allow users to provide a custom error message as the second argument:

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

assert($user->is_authenticated, "User must be logged in");
# => User must be logged in

This makes it easier to understand the context of the failure without inspecting the code.

[coveralls]

Pull Request Test Coverage Report for Build 20029366737

Details

• 59 of 61 (96.72%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 85.202%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/Syntax/Keyword/Assert.xs	57	59	96.61%

Totals
Change from base Build 20005013373:	0.4%
Covered Lines:	190
Relevant Lines:	223

---

💛 - Coveralls