[approved.pl]: Add approved.pl

approved.pl

@@ -0,0 +1,17 @@
+#!/usr/bin/perl
+# Read the contents of flag.txt. You can only use commands in the approved list.
+# Hint: You can supply whatever parameters you like to the command!
+
+my @approved_commands = ("ls", "pwd", "whoami");
+
+while (1) {
+    printf("\n> ");
+    my $command = <STDIN>;
+
+    foreach my $approved_command (@approved_commands) {
+        if ($command =~ /^$approved_command/) {
+            print(`$command`);
+            last;
+        }
+    }
+}