my $cmdToRun = "/path-to/the-c-prog";
system ($cmdToRun) && die "system $cmdToRun - $!\n";

##</code><code>##

my $cmdToRun = "/path-to/the-c-prog";
my @results = `$cmdToRun`;

##</code><code>##

my $cmdToRun = "/path-to/the-c-prog";
open (CMD, "$cmdToRun |") || die "open $cmdToRun - $!\n";
while (<CMD>) {
  # loop through the program output here...
}