my $exe='myprogram.exe';
my $user='tester';
my $pass='lab';
my $cmd=qq|runas /profile /user:$user "$exe"|;
open(FH,"| $cmd")  || die $^E;
print FH $pass;
close(FH);

##</code><code>##

H:\Products\Sandbox>runas.pl
Enter the password for tester:
Attempting to start myprogram.exe as user "GUYBOX\tester" ...
RUNAS ERROR: Unable to run - myprogram.exe
1326: Logon failure: unknown user name or bad password.