Re: does a subroutine exist? defined vs glob

Running it under 5.10 where the subroutine doesn't exist I think suggests an explaination:

C:\test>1135926.pl
$VAR1 = '';
$VAR1 = '';
Goto undefined subroutine &Config::non_bincompat_options at C:/perl64/
+lib/Config_heavy.pl line 1290.
[download]

Ie. It is autoloaded.

Which is confirmed by running it with 5.18 and -d:Trace I get:

>> [0] 1135926.pl                    :    7: pp( Config::non_bincompat
+_options() );
>> [0] C:/perl5.18/perl/lib/Config.pm:   81:     require 'Config_heavy
+.pl';
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:    5: use strict;
...
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:    6: use warnings;
...
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:    7: use vars '%Config';
...
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:   75: our $summary = <<'!
+END!';
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:  108: my $summary_expande
+d;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:  129: local *_ = \my $a;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:  130: $_ = <<'!END!';
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1231: my $i = ord(8);
...
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1233: our $byteorder = jo
+in('', unpack('aaaaaaaa', pack('Q', $i)));
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1234: s/(byteorder=)(['"]
+).*?\2/$1$2$Config::byteorder$2/m;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1236: my $config_sh_len =
+ length $_;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1238: our $Config_SH_expa
+nded = "\n$_" . << 'EOVIRTUAL';
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1244: eval {
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1246:      require 'Confi
+g_git.pl';
>> [0] C:/perl5.18/perl/lib/Config_git.pl:    5: $Config::Git_Data=<<'
+ENDOFGIT';
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1247:      $Config_SH_exp
+anded .= $Config::Git_Data;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1248:      1;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1275: my $prevpos = 0;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1301: *DELETE = *CLEAR = 
+\*STORE; # Typeglob aliasing uses less space
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1342: 1;
>> [0] C:/perl5.18/perl/lib/Config.pm:   82:     goto \&launcher unles
+s $Config::AUTOLOAD =~ /launcher$/;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1338:     undef &AUTOLOAD
+;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl: 1339:     goto \&$Config:
+:AUTOLOAD;
>> [0] C:/perl5.18/perl/lib/Config_heavy.pl:   14:     return split ' 
+', (Internals::V())[1];
[download]

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Comment on Re: does a subroutine exist? defined vs glob Select or Download Code

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Re^2: does a subroutine exist? defined vs glob by Anonymous Monk on Jul 23, 2015 at 16:44 UTC
Yes. To amplify the point about autoloading, try this: `use Config; print "defined before\n" if defined &Config::non_bincompat_options; Config::non_bincompat_options(); print "defined after\n" if defined &Config::non_bincompat_options;` [download] Calling the sub causes it to become defined through autoloading.	[reply] [d/l]
Re^3: does a subroutine exist? defined vs glob by Anonymous Monk on Jul 23, 2015 at 16:54 UTC
... and there's a bit of magic that I hadn't realized before, because you can do the same thing with a coderef. `use Config; my $sub = *Config::non_bincompat_options{CODE}; print "defined before\n" if defined &$sub; $sub->(); print "defined after\n" if defined &$sub;` [download] Same result: not defined before, but defined after.	[reply] [d/l]