strings->can->isa but numbers->can't?

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

Whilst trying to explain to someone the benefits of

eval { $x->isa( $class ) }

to determine if an object belongs in a class, I embarrassingly came across the following behavior, which I could not explain.

use strict;
use warnings;

my $x = 'string';
$x->isa('huh?');
[download]

This, surprisingly, runs without error. If instead, I make $x a number:

use strict;
use warnings;

my $x = 3;
$x->isa('huh?')
[download]

I get the expected error:

Can't call method "isa" without a package or object reference at foo.pl line 5.

Why should a string have access to UNIVERSAL methods while a number doesn't? I've tried this with Perl 5.10.1 and 5.12.2.

Comment on strings->can->isa but numbers->can't? Select or Download Code

Replies are listed 'Best First'.
Re: strings->can->isa but numbers->can't? by moritz (Cardinal) on Apr 26, 2012 at 15:32 UTC
Strings are simply interpreted as package names when you call a method on them. This is how `Foo->new` works in the first place. There is no such provision for numbers, arrays, hashes or subroutines. Perl 6 - the future is here, just unevenly distributed	[reply] [d/l]
Re^2: strings->can->isa but numbers->can't? by djerius (Beadle) on Apr 26, 2012 at 17:37 UTC
Strings are simply interpreted as package names when you call a method on them. This is how `Foo->new` works in the first place. D'oh! Of course! I even use that behavior on occasion. Thanks for the reminder.	[reply] [d/l]
Re: strings->can->isa but numbers->can't? by Anonymous Monk on Apr 26, 2012 at 15:16 UTC
Why should a string have access to UNIVERSAL methods while a number doesn't? Because :) `$ perl -e " package 666; " syntax error at -e line 1, near "package 666;" Execution of -e aborted due to compilation errors.` [download] autobox::Core `$ perl -Mautobox::Core -e " 666->say " 666` [download]	[reply] [d/l] [select]
Re: strings->can->isa but numbers->can't? by ikegami (Patriarch) on Apr 26, 2012 at 15:39 UTC
Elsewhere, Perl will stringify when it wants a string. There's no good explanation as to why it doesn't do that here.	[reply]
Re^2: strings->can->isa but numbers->can't? by Anonymous Monk on Apr 26, 2012 at 18:13 UTC
Elsewhere, Perl will stringify when it wants a string. There's no good explanation as to why it doesn't do that here. Sure there is, 3 is not a valid package or subroutine, name `$ perl -le " package 3; " syntax error at -e line 1, near "package 3;" Execution of -e aborted due to compilation errors. $ perl -le " $3::3 " Bareword found where operator expected at -e line 1, near "$3::3" (Missing operator before ::3?) syntax error at -e line 1, near "$3::3 " Execution of -e aborted due to compilation errors. $ perl -le " sub 3 { 3 } " Illegal declaration of anonymous subroutine at -e line 1.` [download]	[reply] [d/l]
Re^3: strings->can->isa but numbers->can't? by choroba (Cardinal) on Apr 26, 2012 at 22:04 UTC
But, interestingly `perl -le "*3 = sub { 4 };print 3->()" 4` [download]	[reply] [d/l]