#!/usr/bin/perl

use strict;
use warnings;

print "Press Control-C to exit\n";
while (1) {		#do until he requests exit
    print "? ";
    my $x = <STDIN>; #get next expression entered
    $x =~ s{[^()\d+*/%-]}{}ga; #remove any unexpected chars
    print "= " , eval($x) , "\n"; #print the result
}