I have used the B module to display the glob's name which is what I think Sub::Identify uses:

use warnings;
use strict;
use B qw(svref_2object);

sub foo
{
    print "I really do exist!\n";
}

for my $coderef ( \&foo, \&bar ) {
    unless ( defined &$coderef ) {
        printf "could not call %s\n", svref_2object( $coderef )->GV->N
+AME;
    }
}

# A symbol table entry is created for bar
print "$::{ 'foo' }\n$::{ 'bar' }\n";
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