获取perl字符串计算结果 [英] Get the perl string calculation result

问题描述

如果一个字符串如下表示$str = "5+2-1";我想从该字符串中获取计算结果.我如何转换为标量来计算这个?谢谢.

If one string is expressed like below $str = "5+2-1"; I'd like to get the calculation result from that string. How do I convert to scalar to compute this? Thanks.

推荐答案

最简单的方法:

print eval('5+2-1');

但它不安全:

print eval('print "You are hacked"');

您需要在 eval 之前检查字符串.您也可以使用 Math::Expression 模块或来自 cpan 的许多其他模块:

You need to check string before eval it. Also you can use Math::Expression module or many other modules from cpan:

#!/usr/bin/perl

use strict;
use warnings;
use Math::Expression;

my $env = Math::Expression->new;

my $res = $env->Parse( '5+2-1' );

# my $res = $env->Parse( 'print you are hacked' );  # no math expression here

print $env->Eval( $res );

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