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skills/result-simple/SKILL.md

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+---
+name: result-simple-perl
+description: Use Result::Simple for tuple-based error handling in Perl
+version: 1.0.0
+author: kfly8
+tags: [perl, cpan, error-handling, result-type]
+---
+
+# Result::Simple - Tuple-based Error Handling
+
+Result::Simple provides lightweight error handling using tuples `($value, $error)` instead of objects.
+
+## Core Functions
+
+### `ok($value)` / `err($error)`
+```perl
+use Result::Simple qw(ok err);
+
+sub divide {
+    my ($a, $b) = @_;
+    return err('Division by zero') if $b == 0;
+    return ok($a / $b);
+}
+
+my ($result, $error) = divide(10, 2);
+if ($error) {
+    warn "Error: $error";
+} else {
+    print "Result: $result";
+}
+```
+
+## Practical Examples
+
+### Error Chaining Pattern
+```perl
+sub process_config {
+    my $filename = shift;
+    
+    my ($content, $read_error) = read_file($filename);
+    return (undef, $read_error) if $read_error;
+    
+    my $data = eval { decode_json($content) };
+    return err("JSON error: $@") if $@;
+    
+    return ok($data);
+}
+```
+
+### Type Checking with result_for
+```perl
+use Result::Simple qw(ok err result_for);
+use Types::Standard qw(Dict Str);
+use Types::Common::Numeric qw(PositiveInt);
+use kura Error => Dict[message => Str];
+
+# result_for requires structured error type (not plain string)
+result_for calculate => PositiveInt, Error;
+
+sub calculate {
+    my ($a, $b) = @_;
+    # Error must be structured (HashRef)
+    return err({ message => 'Invalid input' }) if $a < 0;
+    return ok($a * $b);
+}
+
+# Set RESULT_SIMPLE_CHECK_ENABLED=1 to activate type checking
+# $ENV{RESULT_SIMPLE_CHECK_ENABLED} = 1;
+
+my ($result, $error) = calculate(5, 3);
+if ($error) {
+    warn "Error: $error->{message}";
+} else {
+    print "Result: $result";  # 15
+}
+
+# Type checking works when RESULT_SIMPLE_CHECK_ENABLED=1
+# calculate(5.5, 3);  # Dies: Invalid success result (Float instead of PositiveInt)
+```
+
+**Important**: `result_for` requires:
+- Type::Tiny objects (not string type names)
+- Structured error type (use `Dict[...]` with kura)
+- Environment variable `RESULT_SIMPLE_CHECK_ENABLED=1` for runtime checking
+