Exercise 1:    \$foo =~ /^[A-G]/

Exercise 2:    \$foo =~ /^[H-N]/

Exercise 3:    \$foo =~ /^\0/

Exercise 4:    \$foo =~ /IO::Handle/

Exercise 5:    \$foo =~ /IO::/ && $foo

Exercise 6:    \$foo[$[] == \$foo[$[+1]