Re^2: What does use vars qw{$VERSION}; do?

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Re^3: What does use vars qw{$VERSION}; do? by davido (Cardinal) on Oct 31, 2016 at 05:15 UTC
All CPAN modules should (and many other non-CPAN modules also do) declare a `$VERSION`. This allows the caller to do this: `use Foo; if (Foo->VERSION() < 1.56) { # do something... } # or if ($Foo::VERSION < 1.56) { # do something... }` [download] (Take your pick.)... or... `use Foo 1.56 # Die during compiletime if the minimum version is not me +t.` [download] In most cases the module that declares a version doesn't use it for anything itself. The package global is set up for external consumption. This is one of the benefits of package globals: Anyone from any other package can reach right in and have a look. Here's another example: `perl -MList::Util -E 'say List::Util->VERSION()'` [download] The `BEGIN` block, once again, is used to assure that the variable is given a value early enough in the compile process that it will be available to the caller when the caller invokes `use`. It also turns out that `use` can be used to enforce minimum versions, so the variable MUST have a value early in the process. See use for additional explanation of version checking, and perlmod and perlmodstyle for discussion of version numbers. Dave	[reply] [d/l] [select]
Re^4: What does use vars qw{$VERSION}; do? by alwynpan (Acolyte) on Oct 31, 2016 at 05:25 UTC
Hi Dave, crystal clear. Thank you so much for your detailed explanation.	[reply]
Re^3: What does use vars qw{$VERSION}; do? by ikegami (Patriarch) on Nov 02, 2016 at 16:25 UTC
Yeah, you could use that instead (since Perl 5.6). There's a corner case in which they are different, but it's nothing to worry about.	[reply]