On Windows, you might try:

In a *nix environment, you could try:

See also: perlipc#Complete Disassociation of Child from Parent, which for a Windows user is going to lead you to Win32::Process

The end result, if you go the Win32::Process route might look something like this:

use Win32::Process;

my $curdir       = 'C:/whatever';
my $appname      = 'whatever.exe';
my $command_line = 'who_knows';
my $p_obj;
Win32::Process::Create( 
    $p_obj, 
    $appname, 
    $command_line, 
    0, 
    CREATE_NEW_CONSOLE | DETACHED_PROCESS | NORMAL_PRIORITY_CLASS, 
    $curdir 
) or die "Couldn't spawn the process.\n";
[download]

...though I'm not certain on the choice of flags.