die "Can't fork: $!" unless defined $pid = open(KID, "-|");
if ($pid) {           # parent
    while (<KID>) {
       # do something
    }
    close KID;
} else {
    exec 'myprog', 'arg1', 'arg2' 
        or die "can't exec myprog: $!";
}

##</code><code>##

Shell Script:

#!/bin/ksh

# print the arguments for checking
# $1 is the directory 
# $2 is the executable 

echo $1
echo $2

# change dir to $1
cd $1

# execute $2
$2

echo "Exit"


##</code><code>##

...
...

$dir = 'some path'; # untainted
$exe = 'some executable'; # untainted
...
...
exec 'unixscript.sh', $dir, $exe
...
...