Perl's RegExp syntax

How would you factorize (or not) the following line ?

if ($Hour =~ /^(\d{2})(\d{2})(\d{2})$/) { $result = "开发者_如何学JAVA$1:$2:$3" }

First off, don't use \d unless you want to match all Unicode digit characters (such as 𝟚 or ᠕). If you want to match zero through nine, you must say [0-9].

Unfortunately, you cannot shorten that to

if ($Hour =~ /^([0-9]{2}){3}$/) { $result = "$1:$2:$3" }

because you care about all of the matches and that will only save the last one. Likewise

if ($Hour =~ /^([0-9]{6})$/) { $result = "$1:$2:$3" }

is out. You could say

($result = $Hour) =~ s/([0-9]{2})(?!$)/$1:/g;

but you would be trading clarity for a slightly shorter line.

Looks pretty good to me as it is.

You can replace each {2} with another \d if you want.

You could use $result=join":",$Hour=~/^(\d\d)/g but it's not as strict - it will match any even-length string of digits at the start of a line.

I would use \z instead of $, unless you really want to allow an optional trailing newline character. Other than that (and the inconsistent capitalization of variables), it's fine.

Looks good. Matching a time can be taken to various level of strictness. The above would allow for something like 999999

Another approach to match a 24-hour clock is to use

([01]?[4-9]|[012]?[0-3])

for the hour-part and then

[0-5][0-9]

for minutes.

or (for the fun of it), the hour-part can also be matched using

([01]?[0-9]|2[0-3])