Although you'd like to run a DOS command, I'd be willing to bet you're running a windows machine. I've had trouble running exec on ActiveState Perl before, so I usually use system instead. For instance, if I wanted to open an XML file that I just finished writing so that I can view the results, I've written in the past:

# open file for output
open my $file, ">${title}.xml" or die "Couldn't open file: $title.xml 
+\n\n";
select $file;

## Print lots of XML data here

# open GGobi for viewing
close $file;
system "ggobi.exe ${title}.xml";
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In addition, if I use system, my Perl scripts waits around until the new process is terminated.