For those who were interested in the problem, I was able to have the "new" code run in a "safe" way by forking... forking copies the symbol table and changes to it in the child process are not mirrored to the parent process.
Here's a quick snippet showing the method... 
use Data::Dumper;
sub foo
{
   if ( open(FROM, "-|" ) )
   {
      # PARENT
      local($/);
      my $output = <FROM>;  # from the child
      my $retval = eval "$output";
      my @values = @$retval;

      return $values[0] if( @values == 1 );
      return @values;
   }
   else
   {
      # CHILD
      unshift( @INC, "/path/to/NEW");
      findAndRequire( 'My::Package' );
      my @output = My::Package::func();

      # local not really needed here, but who is counting
      local $Data::Dumper::Purity = 1;
      local $Data::Dumper::Terse = 1;
      print Dumper( \@output ); # to the parent
      exit;
   }
}

sub findAndRequire 
{
   my ($pkgName) = @_;

    $pkgName =~ s/::/\//g;

   # search @INC for a file which matches
   foreach my $dir (@INC) 
   {
      my $file = "${dir}/${pkgName}.pm";
      if( -e $file )
      {
         require "$file";
         last;
      }
   }
}

# Call our "proxied" function!
my $output = foo();
local $Data::Dumper::Purity = 1;
local $Data::Dumper::Terse = 1;

print "OUTPUT = " . Dumper( $output );

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In reply to Re: How can I (safely) use packages of the same name but different versions? by xevian
in thread How can I (safely) use packages of the same name but different versions? by xevian

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