What are common pitfalls or gotchas with given/when (smartmatch ~~, experimental)?

When using the given/when construct in Perl, which is an experimental feature, there are several common pitfalls you should be aware of. These can affect how your code behaves, especially given the use of smart matching (~~). Below are some of the notable gotchas:

  • Type Mismatches: Smart matching can sometimes produce unexpected results when comparing different types, such as strings and numbers.
  • Array Comparisons: When comparing arrays, the whole array is treated as a single entity, which can lead to confusion if not handled properly.
  • Undefined Values: Using undefined values can yield warnings, and comparing them might lead to unintended behavior.
  • Code Readability: The use of smart matching can obscure the intent of the code, making it harder for others to understand.
  • Behavior Variability: The behavior of smart matching can change between Perl versions, so relying on it can lead to code that breaks in future updates.

Below is a code example demonstrating some of these pitfalls:

#!/usr/bin/perl use v5.10; use strict; use warnings; my $value = '10'; given ($value) { when (10) { say "It's the number 10!" } # This will match due to smart matching. when ('10') { say "It's a string '10'!" } # This can lead to confusion. when (undef) { say "It's undefined!" } # Careful with undefined values. }

Perl given when smartmatch experimental feature pitfalls coding best practices

Related Questions

How do I avoid rehashing overhead with std::set in multithreaded code?

How do I find elements with custom comparators with std::set for embedded targets?

How do I erase elements while iterating with std::set for embedded targets?

How do I provide stable iteration order with std::unordered_map for large datasets?

How do I reserve capacity ahead of time with std::unordered_map for large datasets?

How do I erase elements while iterating with std::unordered_map in multithreaded code?

How do I provide stable iteration order with std::map for embedded targets?

How do I provide stable iteration order with std::map in multithreaded code?

How do I avoid rehashing overhead with std::map in performance-sensitive code?

How do I merge two containers efficiently with std::map for embedded targets?