Just put the parameters behind the call:

system("program.sh $param1 4 $param2");
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or, if you want to get the output of the program into your perl script:

my @result= `program.sh $param1 4 $param2`; #backticks

or

open($f,'-|',"program.sh $param1 4 $param2");
while (my $result= <$f>) {
...
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I prefer to call

system "program.sh", $param1, 4, $param2;
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unless I really want to shell to interpret any special characters.

   $result = system("program param1 param2");