quadratic equation with help flag handling and conditional prompting

cli/exercise_02/quadratic.pl

@@ -0,0 +1,53 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use Math::Complex;
+use File::Basename;
+
+
+my $prog = basename($0);
+my $USAGE = <<USAGE
+Usage: $prog <a> <b> <c>
+USAGE
+;
+
+
+sub quad {
+    my ($a, $b, $c) = @_;
+    my $positive = (
+        ($b * -1) - sqrt(($b ** 2) - (4 * ($a * $c))) / (2 * $a)
+    );
+    my $negative = (
+        ($b * -1) + sqrt(($b ** 2) - (4 * ($a * $c))) / (2 * $a)
+    );
+
+    return ($positive, $negative);
+}
+
+foreach my $arg (@ARGV) {
+    if (($arg eq "-h") || ($arg eq "--help")) {
+        die $USAGE;
+    }
+}
+
+my ($a, $b, $c) = @ARGV;
+if (!defined $a) {
+    print '$a = ';
+    $a = <STDIN>;
+}
+if (!defined $b) {
+    print '$b = ';
+    $b = <STDIN>;
+}
+if (!defined $c) {
+    print '$c = ';
+    $c = <STDIN>;
+}
+
+my @result = quad($a, $b, $c);
+printf("%s, %s\n", $result[0], $result[1]);
+
+
+1;
+__END__