++ to all proposed solutions and explanations.

If I may add my $0.02, there is something to be said for minimising repetition of similar looking code, particularly if it is likely that the number of repetitions may increase. With that in mind, may I offer: 

#!/usr/bin/perl -w
use strict;

my %do_op=(
  add       => sub{$_[0] +  $_[1]},
  multiply  => sub{$_[0] *  $_[1]},
  divide    => sub{$_[0] /  $_[1]},
  subtract  => sub{$_[0] -  $_[1]},
  power       => sub{$_[0] ** $_[1]}, 
  equal      => sub{$_[0] == $_[1]? $_[0]:0},
  max        => sub{$_[0] >  $_[1]? $_[0]:$_[1]}, 
  min        => sub{$_[0] <  $_[1]? $_[0]:$_[1]},        
);

sub operate{ 
        my $op=shift;
        my $tot = shift;           
        while (defined (my $x=shift)){
                   $tot = $do_op{$op}->($tot,$x);
          }
          $tot;
};            

my $op = shift or die "You must specify an operation followed by numbe
+rs.\n";
die "Non-numeric input.\n" if grep /\D/, @ARGV;
die "Invalid operation.\n" unless exists $do_op{$op};

print "$op (@ARGV)= ". operate($op, @ARGV) . "\n";

[download]
Now, you are on your way to implementing a reverse polish engine ...

     "As you get older three things happen. The first is your memory goes, and I can't remember the other two... " - Sir Norman Wisdom

In reply to Re: Simple add and multiply subroutines by NetWallah
in thread Simple add and multiply subroutines by negzero7

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