—John

Make sure that when you say "context", you're not thinking "scalar" and "list" context. Those don't apply here. Read on...

print FOO $bar;
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Puts the contents of $bar on the filehandle FOO. We're all clear on that.

print(FOO $bar);
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Does exactly the same thing in a nicely Perl 4-ish way. Perl's parser knows that the first argument to print (regardless of the parens) might be a filehandle which won't be comma-separated from the first thing to be printed. Now:

print(Package::FOO $bar);
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Falls into the same trap. You're just specifying the package that the filehandle is in. The solutions:

print +(Package::FOO $bar);
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The + tells the parser that the parens don't go with the print (and therefore the Package::FOO) and they're just grouping. So the parser isn't looking for a filehandle anymore. The Package::FOO gets used with indirect object syntax.

print(Package::FOO($bar));
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The parser doesn't see a first-argument space-separated from the things to be printed and knows that Package::Foo is Something Else. (Later it'll know it's a function call.)

print(&Package::FOO $bar);
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Same goes here, the parser doesn't see a filehandle here and knows that it shouldn't go looking here for one.

I hope that helps. More importantly I hope my lack-of-sleep answer didn't cause more questions than answered...

Yes that helps. You say that the parens don't affect it. The "if it looks like a function" rule tells it were the parameter list ends, but the determination that the first argument doesn't have a comma after it must come after that.

So... why doesn't it know that's a function already? The module was "use"d, so it knows what's inside it.

I don't think perl is parsing that as an indirect object... it looks like perl interprets your print call as the two argument form: print FILEHANDLE LIST. I can emulate this with the following code:

#!/usr/bin/perl -wT
use strict;

package main;
print Mymod::mysub ();

package Mymod;
sub mysub { '123' }
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Which errors out with:
print() on unopened filehandle Mymod::mysub at ./parensubtest.pl line 5.

Interestingly enough, if you swap the two stanzas (move lines 7,8 above 4,5) the error disappears.

A similiar (but not identical) issue was discussed at Filehandles vs. Packages: And the winner is...

-Blake

What you call the "two argument form" is the "indirect object". You can have any number of arguments: print (x,y,z,1,2,3);. The "indirect object" is the special argument that doesn't have a comma after it.

I agree, writing print Mymod::mysub (); will look like an indirect object per the node you refered to. But why does print (Mymod::sub ()); that is, with parens around it, do the same thing? That is the question I was asking.