Document the limitations and work arounds of -e.

[Caldrin]

According to the documentation I expect the func keyword to work like this:
perl -e 'use perl5i::2; func test($t) { return $t } print test("test")'

This gives the following error message:
PL_linestr not long enough, was Devel::Declare loaded soon enough in -e at /home/user/perl5/perls/perl-5.16.2/lib/site_perl/5.16.2/x86_64-linux/Devel/Declare/Context/Simple.pm line 71.

When I use the perl5i binary instead of perl like this:
perl5i -e'use perl5i::2; func test($t) { return $t } print test("test")'

I get
Prototype mismatch: sub main::open (*;$@) vs none at /home/user/perl5/perls/perl-5.16.2/lib/site_perl/5.16.2/perl5i/2/UNIVERSAL.pm line 23
test

Only when I use perl5i and remove the "use perli5::2" inside it works as expected.

[schwern]

Thanks for the report.

The PL_linestr error is an unfortunate bug in Devel::Declare which perl5i uses to rewrite Perl syntax. The same problem appears in related modules like Method::Signatures or MooseX::Method::Signatures.

$ perl -e 'use MooseX::Method::Signatures; method test($t) { return $t } print main->test("test")'
PL_linestr not long enough, was Devel::Declare loaded soon enough in -e at /Users/schwern/perl5/perlbrew/perls/perl-5.16.2-threads/lib/site_perl/5.16.2/darwin-thread-multi-2level/Devel/Declare/Context/Simple.pm line 71.

$ perl -e 'use Method::Signatures; method test($t) { return $t } print main->test("test")'
PL_linestr not long enough, was Devel::Declare loaded soon enough in -e at /Users/schwern/perl5/perlbrew/perls/perl-5.16.2-threads/lib/site_perl/5.16.2/darwin-thread-multi-2level/Devel/Declare/Context/Simple.pm line 71.

The Devel::Declare folks have basically said they can't fix it. We should document that limitation.

perl5i -e'use perl5i::2; is throwing a warning because it's effectively importing perl5i into the same namespace twice. That could probably be prevented.

perl -Mperl5i::2 -e works, I think, because Devel::Declare is loaded before Perl sees the -e line and has time to do its magic. The perl5i binary should be doing the equivalent of perl -Mperl5i::2 -e so it should work... and it does.

I see two actions out of this...

• Document the perl -e 'use perl5i::2; ...' limitations and the perl5i -e and perl -Mperl5i::2 -e work arounds.
• Allow loading perl5i::2 multiple times in the same namespace without warning.

I opened #251 for that second one.