#!/usr/bin/perl -w

use strict;

while(<>)
{
    chomp;

    #
    # Stop if the user typed 'exit'.
    #
    last if /^exit$/;

    #
    # Call subroutines parse_line() and calculate() to do the actual work
    #
    my($op, $n1, $n2) = parse_line($_);
    my $result = calculate($op, $n1, $n2);

    #
    # Print the results.
    #
    print "$n1 $op $n2 = $result\n";
}

#
# Now all you have to do is write parse_line() and calculate() so that
# the program will work!
#