#!/usr/bin/perl -w

use strict;
use warnings;

# Test data
my $string = "1 + 9 * ( 60 / 5 )";

# Validate
if ($string !~ m:^[-+*/()0-9.\s]+$:) {
    die "Bad input '$string'\n";
}

my $result = eval $string;
print "Result of '$string' = $result\n";