$My::{$symbol} returns a glob.

*NAME{SLOT} accesses a glob's slot.
*BLOCK{SLOT} accesses a glob's slot.
*$NAME{SLOT} accesses a glob's slot.
EXPR->*{SLOT} accesses a glob's slot.^[1]

So,

my $glob = $My::{$symbol};
$glob && *{ $glob }{CODE}
$glob && *$glob{CODE}
$glob && $glob->*{CODE}
[download]

1. Requires Perl 5.24+. Available in Perl 5.20+ by adding both use feature qw( postderef ); and no warnings qw( experimental::postderef );, or by adding use experimental qw( postderef );.

Something changed in 5.22. $My::{$symbol} can return a code reference or -1 instead of a glob.

The following is therefore needed:

sub get_code_ref_by_fqn {  # Fully qualified name
   my ($fqn) = @_;

   my @pkg_name_parts = split /::/, $fqn;
   my $symbol = pop(@pkg_name_parts);

   my $pkg = \%::;
   for (@pkg_name_parts) {
      $pkg = $pkg->{$_.'::'}
         or return undef;
   }

   my $glob_or_code = $pkg->{$symbol}
      or return undef;

   return $glob_or_code if ref($glob_or_code);
   return undef if ref(\$glob_or_code) ne 'GLOB';
   return *$glob_or_code{CODE};
}
[download]

But you know what, let's just leave those dirty details to Perl.

sub get_code_ref_by_fqn {  # Fully qualified name
   my ($fqn) = @_;
   no strict qw( refs );
   return undef if !defined(&$fqn);
   return \&$fqn;
}
[download]

---

Above tested using

use 5.012;
use warnings;

sub Foo::Bar::y;
sub Foo::Bar::z { }

say get_code_ref_by_fqn('Foo::Bar::x') // '[undef]';
say get_code_ref_by_fqn('Foo::Bar::y') // '[undef]';
say get_code_ref_by_fqn('Foo::Bar::z') // '[undef]';
[download]

This is *exactly* what I was looking for - would you be so kind to rewrite my script above with your syntax (am interested in package "main") as I seem to be too drunk to do it myself and my attempts don't compile...

Main is %:: (or %main:: (or %main::main:: (...))) instead of %My::.