Simple RPN Calculator

rpn_calc.cgi

#!/usr/bin/perl -T

# Web script version:
# Takes RPN strings and computes final value.
# Places numbers on stack, pops last 2 off to compute operation and
# then adds answer onto stack until only one number left in the stack array.

my $operator = '[-+*/^]';

my @tests = ('3 4 + 1 1 + + 3 /','3 4 2 * 1 5 - 2 3 ^ ^ / +');
my @stack;
my $answer;

print "Content-type: text/html\n\n";
print "<h1>RPN Calculator</h1><br>";

foreach $itm (@tests) {
    chomp $itm;
    $itm =~ s/\s+/ /g;
    print "Solving RPN: <i>$itm</i><br><br>";
    @line = split(/ /, $itm);
    foreach $line_item (@line) {
        #print "\$line_item = $line_item <br>";
        if ( $line_item =~ /\d+/ ) {
            push(@stack, $line_item);
            #print "added $line_item to stack <br><br>";
        }
        elsif ( $line_item =~ /($operator)/ ) {
            $y = pop(@stack);
            $x = pop(@stack);
            if ($1 eq '*') {
                $answer = $x * $y;
            }
            elsif ($1 eq '-') {
                $answer = $x - $y;
            }
            elsif ($1 eq '+') {
                $answer = $x + $y;
            }
            elsif ($1 eq '/') {
                $answer = $x / $y;
            }
            elsif ($1 eq '^') {
                $answer = $x ** $y;
            }
            push(@stack, $answer);
            #print "added $answer to stack <br>";
            print "operation: $x $1 $y = $answer <br>";
        }
    }
    $x = pop(@stack);
    print "<br><b>Final Answer = " . $x . '</b><br><br><br>';

}