IIRC, you need to pass the parameter with quotes, as the shell will split on whitespace otherwise...

[Perl Program]
$testprog = "testprog";
$a=1;
$b=2;
$c="\"This is a test\"";
system($testprog $a $b $c)
... 

[in Shell script "testprog"]
a=$1
b=$2
c=$3
echo $a = 1
echo $b = 2
echo $c = "This is a test"
[download]

--
RatArsed