Interesting question! If I've understood correctly, you want to remove a subroutine alias, without actually undefining the subroutine itself. The only way I can think of to do that is: 
# Usage: unalias ($package, $name)
# Will remove the subroutine entry from the package's glob
sub unalias {
    my ($package, $name) = @_;
    no strict;    # Disable the safety systems
    local *temp;  # Make a local glob
    
    my $glob = ${"${package}::"}{$name};  # Grab the glob
    *temp = *$glob{SCALAR};    # Copy the scalar part
    *temp = *$glob{ARRAY}  if defined *$glob{ARRAY};
    *temp = *$glob{HASH}   if defined *$glob{HASH};
    *temp = *$glob{IO}     if defined *$glob{IO};
    *temp = *$glob{FORMAT} if defined *$glob{FORMAT};
    
    ${"${package}::"}{$name} = *temp;
}

[download]
That seems to do what you asked for. So you can use File::Copy, and then at some point unalias('main', 'copy'); and the alias is removed. Is that what you meant?

In reply to Re: version based compilation by robin
in thread version based compilation by steves

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