Effective Perl Programming – write better, more idiomatic Perl
Before Perl v5.10 introduced state variables, people did various things to create persistent lexical variables for a subroutine. With v5.30, one of those constructs is now a fatal error.
Often you want a persistent variable to be scoped and private to a subroutine. But, once you leave that scope, normal lexical variables disappear because their reference count drops to zero. So, no persistence.
Continue reading “No more false postfix lexical declarations in v5.30”
Two features that I have previously discouraged are now gone from Perl. The lexical $_ and auto dereferencing.
The lexical $_ was a consequence of the way Perl wanted smart match to work. In a given-when, instead of aliasing $_ like foreach does, the block had an implicit my $_ = .... This interfered with the package version, as I wrote about in Use for() instead of given() and Perl v5.16 now sets proper magic on lexical $_. Continue reading “Lexical $_ and autoderef are gone in v5.24”
[Lexical $_ was removed in v5.24]
Perl v5.10 introduced given and the lexical $_. That use of $_, which everyone has assumed is a global variable, turned out to be a huge mistake. The various bookkeeping on the global version didn’t happen with the lexical version, so strange things happened. Continue reading “Perl v5.16 now sets proper magic on lexical $_”
[Update: Perl v5.24 removes this experimental feature, for the reasons I list, among others.]
Perl 5.14 added an auto-dereferencing features to the hash and array operators, and I wrote about those in Use array references with the array operators. I’ve never particularly liked that feature, but I don’t have to like everything. Additionally, Perl 5.12 expanded the job of keys and values to also work on arrays. Continue reading “Don’t use auto-dereferencing with each or keys”
[Lexical $_ was removed in v5.24]
Perl 5.10 introduced the given-when feature, a fancier version of the C switch feature. However, it was poorly designed and tested and depended on two other dubious features, the lexical $_ and smart-matching. Parts of this feature are salvageable, but you should avoid the literal given (and probably the lexical $_ and the smart matching, but I’ll skip those for this Item). Continue reading “Use for() instead of given()”