I was reading HOP and it got me thinking about inline caching methods. Assuming the no-false-values constraint is not a problem, there's an easy and efficient way to add caching to a sub that returns a scalar (replace the join as needed): 
my %foo_cache;
sub foo {
   $foo_cache{join ",", @_} ||= do {
      ... rest of sub goes here
   }
}

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(If you have it enabled, //= is even better.)

But what about when the function generates a list? Easy enough: 

my %foo_cache;
sub foo {
   @{$foo_cache{join ",", @_} ||= [ do {
      ... rest of sub goes here
   }]}
}

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But that changes the result in scalar context if an actual list is returned. The fix is a little expensive: 
my %foo_cache;
sub foo {
   return @$_[0..$#$_] for $foo_cache{join ",", @_} ||= [ do {
      ... rest of sub goes here
   }]
}

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Can anybody suggest a less expensive alternative? Pity there's no list keyword.

In reply to inline caching a list-generating sub by ysth

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