First, it must be $site, not site. Next. You must use backslaches with $prog,. Finally, if the program call itself includes the executable without the path, it works.

#!/usr/bin/perl

use Win32::Process;

my $prog="C:\\Programme\\Internet Explorer\\iexplore.exe";
my $site="http://www.gmx.de";

Win32::Process::Create($ProcessObj,$prog,'iexplore "' . $site . '"', 0
+, NORMAL_PRIORITY_CLASS, ".");
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Check the Task Manager to see, if the iexplorer did start! See the Win32::Process pod, too:

        sub ErrorReport{
                print Win32::FormatMessage( Win32::GetLastError() );
        }

        Win32::Process::Create($ProcessObj,
                                "D:\\winnt35\\system32\\notepad.exe",
                                "notepad temp.txt",
                                0,
                                NORMAL_PRIORITY_CLASS,
                                ".")|| die ErrorReport();

        $ProcessObj->Suspend();
        $ProcessObj->Resume();
        $ProcessObj->Wait(INFINITE);
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