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theory.pm

Lexical Subroutines

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Ricardo Signes:

One of the big new experimental features in Perl 5.18.0 is lexical subroutines. In other words, you can write this:

my sub quickly { ... }
my @sorted = sort quickly @list;

my sub greppy (&@) { ... }
my @grepped = greppy { ... } @input;

These two examples show cases where lexical references to anonymous subroutines would not have worked. The first argument to sort must be a block or a subroutine name, which leads to awful code like this:

sort { $subref->($a, $b) } @list

With our greppy, above, we get to benefit from the parser-affecting behaviors of subroutine prototypes.

My favorite tidbit about this feature? Because lexical subs are lexical, and method-dispatch is package-based, lexical subs are not subject to method lookup and dispatch! This just might alleviate the confusion of methods and subs, as chromatic complained about just yesterday. Probably doesn’t solve the problem for imported subs, though.

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