blocks|key|763559|text|您不应该使用正则表达式来进行数值范围验证。您需要的正则表达式为：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|763560|/%5E(\d%2B)$/|code-block|syntax|javascript|763561|然后,|763562|if+($1+>=+1+&&+$1+<=+12)+{
++++#+valid+month
}|763563|这比任何用于验证数值范围的正则表达式都更容易阅读。|763564|另外，Perl通过在目标中搜索匹配的表达式来计算正则表达式。所以：|763565|/(0[1-9]%7C1[012])/|763566|搜索后跟1到9的0，或后跟0、1或2的1。这将匹配"202“等许多其他数字。另一方面：|763567|/(0?[1-9]%7C1[012])/|763568|搜索可选的0+1到9，或者1后跟0、1或2。因此，"13“在这里匹配，因为它包含1，与正则表达式的前半部分匹配。要使您的正则表达式按您期望的方式工作，|763569|/%5E(0?[1-9]%7C1[012])$/|763570|%5E和$分别将搜索定位到字符串的开头和结尾。|offset|length|style|CODE|763571|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|1|2|1|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|18|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1A|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|1B|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|1C|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|1D|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|1E|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|1F|8|@]|9|@]|A|$]]|$1|W|3|X|5|D|7|1G|8|@]|9|@]|A|$E|F]]|$1|Y|3|Z|5|6|7|1H|8|@$10|1I|11|1J|12|13]|$10|1K|11|1L|12|13]]|9|@]|A|$]]|$1|14|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|15|$]]

You shouldn't use a regular expression to do numeric range validation. The regular expression you want is:

<pre><code>/^(\d+)$/
</code></pre>

Then,

<pre><code>if ($1 &gt;= 1 &amp;&amp; $1 &lt;= 12) {
 # valid month
}
</code></pre>

This is much easier to read than any regular expression to validate a numeric range.

As an aside, Perl evaluates regular expressions by searching within the target for a matching expression. So:

<pre><code>/(0[1-9]|1[012])/
</code></pre>

searches for a 0 followed by 1 to 9, or a 1 followed by 0, 1, or 2. This would match "202" for example, and many other numbers. On the other hand:

<pre><code>/(0?[1-9]|1[012])/
</code></pre>

searches for an optional 0 1 to 9, or a 1 followed by 0, 1, or 2. So "13" matches here because it contains a 1, matching the first half of the regex. To make your regular expressions work as you expect,

<pre><code>/^(0?[1-9]|1[012])$/
</code></pre>

The <code>^</code> and <code>$</code> anchor the search to the start and end of the string, respectively.

blocks|key|15831|text|如果您真的喜欢使用正则表达式，则需要将%5E和$放入，如|type|unstyled|depth|inlineStyleRanges|entityRanges|data|15832|"%5E(0?[1-9]%7C1[012])$"|offset|length|style|CODE|15833|它不会匹配13，14....|15834|entityMap^0|0|0|K|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

If you really like to use regex, you need to put ^ and $, like

<code>"^(0?[1-9]|1[012])$"</code> 

it will not match 13, 14 ....

blocks|key|2404144|text|给你提示-月份数字"120“也与你的版本匹配:-)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2404145|更改：|2404146|my+$month+=+"(0[1-9]%7C1[012])";|code-block|syntax|javascript|2404147|至|2404148|my+$month+=+/%5E(0[1-9]%7C1[012])$/;|2404149|然后玩得更多|2404150|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

To give you hint - month number "120" also matches in your version :-)

Change:

<pre><code>my $month = "(0[1-9]|1[012])";
</code></pre>

to

<pre><code>my $month = /^(0[1-9]|1[012])$/;
</code></pre>

and then play more with it

blocks|key|764029|text|这里有一种方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|764030|while(1){
++++print+"Enter+in+a+month:+";
++++$pattern+=+<STDIN>;
++++chomp($pattern);
++++if+($pattern+=~+/%5E(Q%7Cq)$/+){last;}
++++if+($pattern+=~+/%5E[0-9]$/+%7C%7C+$pattern+=~+/%5E[0-9][12]$/+)+{
++++++++print+"Pattern+matches\n";
++++}else{
++++++++print+"try+again\n";
++++}
}|code-block|syntax|javascript|764031|输出|764032|$+perl+perl.pl
Enter+in+a+month:+01
Pattern+matches
Enter+in+a+month:+000
try+again
Enter+in+a+month:+12
Pattern+matches
Enter+in+a+month:+00
try+again
Enter+in+a+month:+02
Pattern+matches
Enter+in+a+month:+13
try+again
Enter+in+a+month:|764033|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

here's one way

<pre><code>while(1){
 print "Enter in a month: ";
 $pattern = &lt;STDIN&gt;;
 chomp($pattern);
 if ($pattern =~ /^(Q|q)$/ ){last;}
 if ($pattern =~ /^[0-9]$/ || $pattern =~ /^[0-9][12]$/ ) {
 print "Pattern matches\n";
 }else{
 print "try again\n";
 }
}
</code></pre>

output

<pre><code>$ perl perl.pl
Enter in a month: 01
Pattern matches
Enter in a month: 000
try again
Enter in a month: 12
Pattern matches
Enter in a month: 00
try again
Enter in a month: 02
Pattern matches
Enter in a month: 13
try again
Enter in a month:
</code></pre>

blocks|key|994959|text|不要使用正则表达式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|994960|Perl能够根据上下文自动计算为数字或字符串。01-09在数值上下文中的计算结果为1-9。因此，您可以简单地检查一个值：|994961|print+"Enter+in+a+month:+";
chomp($pattern+=+<STDIN>);
#+We+only+want+to+print+if+the+pattern+matches
print+"Pattern+matches\n"+if+($pattern+<+13+&&+$pattern+>+0);|code-block|syntax|javascript|994962|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Don't use regular expressions. 

Perl has the ability to automatically evaluate as a number or a string based on context. 01-09 will evaluate to 1-9 in the numeric context. So, you can simply check for a value: 

<pre><code>print "Enter in a month: ";
chomp($pattern = &lt;STDIN&gt;);
# We only want to print if the pattern matches
print "Pattern matches\n" if ($pattern &lt; 13 &amp;&amp; $pattern &gt; 0);
</code></pre>

blocks|key|2404204|text|[%5Ed>12%7Cd<0]+OR+%5E[d>12%7Cd<0]|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2404205|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

blocks|key|15921|text|(01-9%7C1012)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|15922|括号是这样的，因此您可以在另一个块中使用它，例如，如果匹配整个yyyy-MM-dd日期格式|15923|来源：http://www.regular-expressions.info/dates.html|offset|length|15924|entityMap|0|LINK|mutability|MUTABLE|url|http://www.regular-expressions.info/dates.html^0|0|0|3|1A|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

(0[1-9]|1[012])

the parens are so you can use this inside another block, for example if matching for an entire yyyy-MM-dd date format

source: <a href="http://www.regular-expressions.info/dates.html" rel="nofollow">http://www.regular-expressions.info/dates.html</a>

blocks|key|995040|text|"%5E(1[012]%7C0?[1-9])$"会更好，因为正则表达式首先被评估。假设你想匹配'12‘，并且你写了"%5E(0?[1-9]%7C1[012])$"，那么'1’将被选中，因为0?[1-9]是最先被取的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|995041|entityMap^0|0|K|1H|K|2E|7|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

<code>"^(1[012]|0?[1-9])$"</code>
would be better because regular expression is assessed first one first. Let's say you want to match '12' and you write <code>"^(0?[1-9]|1[012])$"</code>, then '1' will be picked because <code>0?[1-9]</code> is taken first.

blocks|key|764122|text|要测试month+/+year：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|764123|%5E(0?[1-9]%7C1[012])\/([2-9][0-9)]{3})$|code-block|syntax|javascript|764124|entityMap^0|3|5|B|4|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

To test <code>month</code> / <code>year</code> : 

<pre><code>^(0?[1-9]|1[012])\/([2-9][0-9)]{3})$
</code></pre>

I am setting up this example Perl snippet to validate for months in a date:

Some scenarios I want to accept are:

MM
M

<pre><code>#!/usr/bin/perl
use strict;
use warnings;

my $pattern;
my $month = "(0[1-9]|1[012])";
my $day = "(0[1-9]|[12]\d|3[01])";

system("cls");

do {

 print "Enter in a month: ";
 chomp($pattern = &lt;STDIN&gt;);

 # We only want to print if the pattern matches
 print "Pattern matches\n" if ($pattern =~ /$month/);


} while ($pattern ne "Q");
</code></pre>

When I run this, it correctly filters from 01-12 but when I change the regex to:

<pre><code>$month = "(0?[1-9]|1[012])";
</code></pre>

then the regex allows 13, 14, etc... what gives?

How can I use a regular expression to validate month input?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在设置这个示例Perl代码片段，以便在一个日期中验证几个月：我想要接受的一些场景是：MM M#!/usr/bin/perluse strict;use warnings;my $pattern;my $month = "(0[1-9]|1[012])";my $day = "(0[1-9]|[12]\d|3[01]...

问如何使用正则表达式验证月份输入？
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问如何使用正则表达式验证月份输入？EN