This should be equivalent:

use B;
sub codename {
    my $coderef = shift;
    return unless ref $coderef eq 'CODE';
    my $cv = B::svref_2object($coderef);
    return $cv->GV->NAME;
}
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But personally I would use Sub::Identify.

use Sub::Identify qw(sub_name);
sub foo {}
print sub_name(\&foo);
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