Lesson 35 of 55
9 mins readAnonymous Subroutines & Closures
In Plain English
Perl supports first-class functions: `my $fn = sub { ... };`. An anonymous subroutine that captures variables from its enclosing scope is a closure.
Deep Dive: How It Works
Code Reference: `my $sub_ref = sub { my $msg = shift; print "$msg\n"; };` called as `$sub_ref->("Hi")`.
Closures: Retain access to private lexical variables even after the parent scope has exited.
Factory Pattern: Generating configured math or validator functions on the fly.
Core Rules to Remember
Code Reference (->()): Invoke a code reference using arrow syntax: `$coderef->($arg)`.
Closures Encapsulate State: Encapsulate private state without global variables.
Live Interactive Example
Hit Run Code to see it liveGenerating Counters with Closures
Python 3.12
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Output Console
Click "Run Code" to view the rendered output.
How it works: Each closure maintained its own isolated $count variable.
Your Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Micro Exercise
Build Multiplier Closure
- Write `sub make_multiplier { my $factor = shift; return sub { my $n = shift; return $n * $factor; }; }`
- Create `my $triple = make_multiplier(3);` and print `"Triple 7: " . $triple->(7) . "\n"`.
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Sandbox Output
Click "Run & Check" to test your solution.
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