Re: subroutine refs

[broquaint]

in reply to subroutine refs

You can safely create a reference to a subroutine by name and the execute that e.g

use strict;

sub dynamic {
  print "Mmm, dynamic.\n";
}

my $name   = 'dynamic';
my $subref = \&$name;
&$subref();

[blokhead]

I find this very surprising. But I checked it and it apparently works.

Why does this give an error:

use strict;
sub dynamic { print "hello\n"; }

my $name = "dynamic";
&$name();

.. and yet this is ok? (they differ only in the last line)

use strict;
sub dynamic { print "hello\n"; }

my $name = "dynamic";
&{ \&$name }();

Before seeing this, I would have bet anything that the &{\&{ ... }} operation was absolutely the same as &{...} (barring weird action-at-a-distance caused by tying, overloading, etc). In fact, I'm not sure whether to consider this a bug or not. Indeed, what is \&$name doing other than "using string as a subroutine ref", which is outlawed under strict refs?

Yet a similar idea with other kinds of refs doesn't do this. Both of these examples fail under strict refs (in my mind because @{\@{...}} is unconditionally the same thing as @{...} ):

use strict;
our @dynamic = ("hello\n");

my $name = "dynamic";
print @$name;

use strict;
our @dynamic = ("hello\n");

my $name = "dynamic";
print @{ \@$name };

My conclusion is that there is an important distinction between naming a subroutine and invoking it, which is manifested bizarrely by different behaviors in the \&{blah} and &{blah} mechanisms.