I think the thing is that use Module (); is a unique case, as the docs highlight: "Again, there is a distinction between omitting LIST (import called with no arguments) and an explicit empty LIST () (import not called)." I think that the LIST in use Module VERSION LIST; is passed to the Module->import(LIST) method using Perl's normal argument list handling, meaning that empty lists will be flattened. This includes everything after the "if" in use if CONDITION, MODULE => ARGUMENTS;.

$ cat Foo.pm 
package Foo;
use warnings;
use strict;
use Data::Dump 'pp';
our $VERSION = 1.23;
sub import { print "import ".pp(\@_)."\n" }
1;
$ perl -wMstrict -e 'use Foo ()'
$ perl -wMstrict -e 'use Foo'
import ["Foo"]
$ perl -wMstrict -e 'use Foo "bar"'
import ["Foo", "bar"]
$ perl -wMstrict -e 'use Foo 1.20 "bar"'
import ["Foo", "bar"]
$ perl -wMstrict -e 'use Foo "bar", "quz"'
import ["Foo", "bar", "quz"]
$ perl -wMstrict -e 'use Foo "bar", ()'
import ["Foo", "bar"]
$ perl -wMstrict -e 'use Foo "bar", (), "quz"'
import ["Foo", "bar", "quz"]
$ perl -wMstrict -e 'use Foo "CONDITION", "MODULE" => "ARGUMENTS"'
import ["Foo", "CONDITION", "MODULE", "ARGUMENTS"]
$ perl -wMstrict -e 'use Foo "CONDITION", "MODULE"'
import ["Foo", "CONDITION", "MODULE"]
$ perl -wMstrict -e 'use Foo "CONDITION", "MODULE" => ()'
import ["Foo", "CONDITION", "MODULE"]

[download]

So if's behavior isn't really surprising, but I agree that its docs could mention this. As ikegami said, it's the perfect chance to get a patch in :-)

Personally I wouldn't mind the workaround BEGIN { require Module if CONDITION }, but you're right about the doc issue.

In reply to Re: 'if' pragma and modules with an empty import list by haukex
in thread 'if' pragma and modules with an empty import list by kcott

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