Re: Use of "Use 5.XXX" pragma

[davido]

It's a little complicated because Perl 5.16 slightly upgraded what the use VERSION pragma does. From the Perl 5.14.2 documentation for use:

Also, if the specified Perl version is greater than or equal to 5.9.5, use VERSION will also load the feature pragma and enable all features available in the requested version.

And then in the Perl 5.16 documentation for use:

use VERSION also enables all features available in the requested version as defined by the feature pragma, disabling any features not in the requested version's feature bundle.

In the perl5160delta documentation we're told:

As of this release, version declarations like use v5.16 now disable all features before enabling the new feature bundle.

So if your Perl interpreter is from the 5.14.x era, you get the older behavior, and if it's from the 5.16.x era or newer (unless it gets changed again) you get the newer behavior. Practically speaking, in either case, use 5.010000;, or use 5.014000;, or use 5.016000; will result in all of the modern features of version 5.10, 5.14, or 5.16 respectively being enabled.

[tobyink]

use 5.016;
use Try::Tiny;

say fc("Hello World");

try {
    use 5.010;
    # Now 5.16-specific features are actually disabled!
    say fc("Hello World");
}
catch {
    my $e = shift;
    warn "FAILED: $e";
};

say fc("Goodnight!");