Re: Anonymous subroutines (why and what for)

[LanX]

There are various possible reasons

In general anonymous subs ...

• don't pollute the namespace - i.e. block a name (sic) in a package
• are private * and scoped when assigned to my var
• don't need to be \& referenced before being passed around ²
• are "created" on the fly at run time °
• can be generated multiple times with binding to different closure vars
• can be nested *
• can easily be used as "lambdas" with map-like functions(&) ³
• (add more techniques from functional programming)
• (add more techniques from metaprogramming)
• ...

Without more details it's hard to tell, why you saw, what you saw.

°) well "available", they are only compiled once at compile time, but their time window/life span is dynamic

*) even in older Perl versions

²) e.g. as callbacks

³) like in List::Util et.al.

Update

Disclaimer: The listed points are not exclusive and have overlaps. Neither do I expect them to be exhaustive and to cover all cases.

[jdporter]

I believe this is an excellent summary. Thanks, LanX!

One context in which I've seen anonymous subs used a lot is where you have code chunks being defined within, and called by, a framework. Execution of the code takes the form of eval'ing the code, so it has lexical context just like a sub. If, in such a code chunk, you want to define a sub so you can call it multiple times (or any other reason), you have to do it as an anonymous sub, since you can't do it any other way (at least not without getting a "won't stay shared" warning). (But your other comment is important too.)

[LanX]

Thanks!

I'm not sure I've ever worked with such kind of a "code template system" ° but I wanted to add metaprogramming anyway. (Done)

°) maybe apart the monastery's codebase ;)

[jdporter]

;-)