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