package magic or am I missing something?

vladb has asked for the wisdom of the Perl Monks concerning the following question:

As the saying goes, "Forever live, forever learn." (I'm not entirely sure if the wording is right, though ;). Even having reached the level of saint, doesn't imply that one is a trully accomplished all-knowing Perl hacker. From time to time, things that I find hard to explain do happen.

Just today, I was coding away happily until I came upon an error message saying

Can't locate object method "try" via package FOO

(note: FOO is a hypothetical package.. ).

When I looked at the code, I noticed that I really wanted to have 'eval' instead of 'try' there. So, I made the correction and went on. However, immediately, I thought "Home come Perl was looking for method 'try' in package FOO?". Indeed, could anyone explain to me the 'magic' (if only there's anything 'magical' about it :) behind this? How is it possible to invoke a package method like in the code provided below?:

use strict;

package FOO;

sub new {};

sub try {
    print "Trying...?\n";
}

package main;

try {
  new FOO;
};
[download]

And the output, of course, is:

Trying...?
[download]

I appreciate your help ;).

_____________________

# Under Construction
[download]

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Re: package magic or am I missing something? by janx (Monk) on Jun 18, 2002 at 20:00 UTC
That's a good one. It's a wonderful example of indirect object syntax. See The Bag'o'Tricks. Use B::Deparse shows what happens: Update: Rather perl -MO=Deparse shows what happens: `sub FOO::new { package FOO; use strict 'refs'; } sub FOO::try { package FOO; use strict 'refs'; print "Trying...?\n"; } use strict 'refs'; do { 'FOO'->new }->try;` [download] As you see, the `do { 'FOO'->new }` [download] gives you the object, which you can happily call a method on ;-) Kay	[reply] [d/l] [select]

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Re: package magic or am I missing something?
by janx (Monk) on Jun 18, 2002 at 20:00 UTC

It's a wonderful example of indirect object syntax. See The Bag'o'Tricks.
Use B::Deparse shows what happens:
Update: Rather

perl -MO=Deparse

sub FOO::new {
    package FOO;
    use strict 'refs';
    
}
sub FOO::try {
    package FOO;
    use strict 'refs';
    print "Trying...?\n";
}
use strict 'refs';
do {
    'FOO'->new
}->try;
[download]

As you see, the

do { 'FOO'->new }
[download]

Kay

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