Might as well toss this in, then: 

...
my $op = shift or die "You must specify an operation followed by numbe
+rs.\n";
###########################################################
die "At least two numbers required.\n" unless @ARGV > 1;
###########################################################
die "Non-numeric input.\n" if grep /\D/, @ARGV;
...

[download]

Despite jwkrahn's warning, I'd want to implement an "eval" wrapped around the operation, too - after carefully vetting the data. It's quite nice for those "Divide by zero" errors. 


-- 
Human history becomes more and more a race between education and catastrophe. -- HG Wells

In reply to Re^2: Simple add and multiply subroutines by oko1
in thread Simple add and multiply subroutines by negzero7

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