Write a program that computes the area of a rectangular.

• Start by having two hard coded values. Multiply them and print the result. The result should be 42:

  $ perl example.pl
  42
  

• Then change the code to prompt the user for two numbers. Multiply them and print the result:

  $ perl example.pl
  First number: 7
  Second number: 6
  42
  
  # ruby example.rb
  First number: 3
  Second number: 11
  33
  

• Further modify the program to warn if one of the numbers given was negative.

  $ python example.py
  First number: 3
  Second number: -1
  Warning: Invalid input. The side of a rectangular cannot be negative.