Query about barewords

[kevinp]

While putting together some examples of using Gtk and Perl I came across the following behaviour which I hope someone can explain.

This piece of code complains of a BAREWORD under strict.

$switch->signal_connect( notify::active => \&toggle );

As you would expect, if I add some quotes the code works with no complaints.

$switch->signal_connect( 'notify::active' => \&toggle );

So - my question is - why does the following work and not complain about barewords.

$update_button->signal_connect ( clicked => \&update );

It seems that Perl sees notify::active and clicked differently and that seems inconsistent to my mind.

Can someone explain the behaviour?

[Athanasius]

From Comma Operator:

The => operator is a synonym for the comma except that it causes a word on its left to be interpreted as a string if it begins with a letter or underscore and is composed only of letters, digits and underscores.

Hope that helps,

[johngg]

Empirically, the documentation seems to be a little inaccurate as the fat comma also seems to work if the word on the left starts with a number and consists only of numbers.

$ perl -Mstrict -Mwarnings -MData::Dumper -E '
> my %hash = (
>    1  => q{one},
>    11 => q{eleven}
>    );
> print Data::Dumper->Dumpxs( [ \ %hash ], [ qw{ *hash } ] );'
%hash = (
          '11' => 'eleven',
          '1' => 'one'
        );
$
$ perl -Mstrict -Mwarnings -MData::Dumper -E '
> my %hash = (
>    1  => q{one},
>    11 => q{eleven},
>    2t => q{fruity},
>    );
> print Data::Dumper->Dumpxs( [ \ %hash ], [ qw{ *hash } ] );'
syntax error at -e line 5, near "2t"
Execution of -e aborted due to compilation errors.
$
$ perl -Mstrict -Mwarnings -MData::Dumper -E '
> my %hash = (
>    1   => q{one},
>    11  => q{eleven},
>    _2t => q{fruity},
>    );
> print Data::Dumper->Dumpxs( [ \ %hash ], [ qw{ *hash } ] );'
%hash = (
          '11' => 'eleven',
          '1' => 'one',
          '_2t' => 'fruity'
        );
$

I hope this is of interest.

[runrig]

...if the word on the left starts with a number and consists only of numbers.

As long as you don't want to keep any leading zeros.

[runrig]

The "bareword" may also start with a "-".

[johngg]

It seems to treat as an octal number, converts to decimal and then stringifies by the look of it.

$ perl -Mstrict -Mwarnings -MData::Dumper -E '
> my %hash = (
>    011 => q{nine},
>    11  => q{eleven},
>    _2t => q{fruity},
>    );
> print Data::Dumper->Dumpxs( [ \ %hash ], [ qw{ *hash } ] );'
%hash = (
          '11' => 'eleven',
          '_2t' => 'fruity',
          '9' => 'nine'
        );
$
$ perl -Mstrict -Mwarnings -MData::Dumper -E '
> my %hash = (
>    08  => q{eight},
>    11  => q{eleven},
>    _2t => q{fruity},
>    );
> print Data::Dumper->Dumpxs( [ \ %hash ], [ qw{ *hash } ] );'
Illegal octal digit '8' at -e line 3, at end of line
Execution of -e aborted due to compilation errors.
$

A zero on its own is fine.

Update: I'm an idiot, I meant to post as a reply to this :-(

[remiah]

Hello.

"clicked" may be a constant. It maybe imported when you declare to use some module.

#!/usr/bin/perl
use warnings;
use strict;

package notify;
use constant {
    active => 2,
};
1;

package main;
use constant {
    clicked=>1,
};

print clicked . "\n";
print notify::active . "\n";

exit;

So, currently, you don't have package "notify" declaring "active" is a constant. If I am looking different direction, forgive me please.