If you look at at the source you'll see FindBin first expands symlinks using readlink, and then runs the result through Cwd::abs_path which does the exact same thing. Brilliant isn't it?

update:

sub File::Spec::dirname {
    my $self = shift;
    return $self->catpath( ( $self->splitpath(shift) )[ 0, 1 ] );
}
sub File::Spec::basename {
    my $self = shift;
    return $self->catpath( ( $self->splitpath(shift) )[ -1 ] );
}
sub File::Spec::realpath {
    my $self = shift;
    require Cwd;
    return $self->canonpath( Cwd::realpath(@_) );
}
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