%vars = (
   FTPPath      => '/my/ftp/path',
   TransferMode => 'ASCII',
);

s/(\$(\w+|{(\$|\w+)}))/
   my $var = defined($3) ? $3 : $2;
   $var eq '$' ? '$' : (defined($vars{$var}) ? $vars{$var} : $1);
/eg;

##</code><code>##

%vars = (
   FTPPath      => '/my/ftp/path',
   TransferMode => 'ASCII',
);

foreach (
   'cd $FTPPath',
   'type ${TransferMode}',
   '${$}escaped!',
) {
   my $command = $_;
   $command =~ s/(\$(\w+|{(\$|\w+)}))/
      my $var = defined($3) ? $3 : $2;
      $var eq '$' ? '$' : (defined($vars{$var}) ? $vars{$var} : $1);
   /eg;

   print("$command\n");
}

__END__
ourput
======
cd /my/ftp/path
type ASCII
$escaped!