regex - Perl - Regex to extract only the comma-separated strings

Question

I have a question I am hoping someone could help with...

I have a variable that contains the content from a webpage (scraped using WWW::Mechanize).

The variable contains data such as these:

$var = "ewrfs sdfdsf cat_dog,horse,rabbit,chicken-pig"
$var = "fdsf iiukui aawwe dffg elephant,MOUSE_RAT,spider,lion-tiger hdsfds jdlkf sdf"
$var = "dsadp poids pewqwe ANTELOPE-GIRAFFE,frOG,fish,crab,kangaROO-KOALA sdfdsf hkew"

The only bits I am interested in from the above examples are:

@array = ("cat_dog","horse","rabbit","chicken-pig")
@array = ("elephant","MOUSE_RAT","spider","lion-tiger") 
@array = ("ANTELOPE-GIRAFFE","frOG","fish","crab","kangaROO-KOALA")

The problem I am having:

I am trying to extract only the comma-separated strings from the variables and then store these in an array for use later on.

But what is the best way to make sure that I get the strings at the start (ie cat_dog) and end (ie chicken-pig) of the comma-separated list of animals as they are not prefixed/suffixed with a comma.

Also, as the variables will contain webpage content, it is inevitable that there may also be instances where a commas is immediately succeeded by a space and then another word, as that is the correct method of using commas in paragraphs and sentences...

For example:

Saturn was long thought to be the only ringed planet, however, this is now known not to be the case. 
                                                     ^        ^
                                                     |        |
                                    note the spaces here and here

I am not interested in any cases where the comma is followed by a space (as shown above).

I am only interested in cases where the comma DOES NOT have a space after it (ie cat_dog,horse,rabbit,chicken-pig)

I have a tried a number of ways of doing this but cannot work out the best way to go about constructing the regular expression.

score 8 · Accepted Answer

怎么样

[^,\s]+(,[^,\s]+)+

这将匹配一个或多个不是空格或逗号的字符，[^,\s]+后跟一个逗号和一个或多个不是空格或逗号的字符，一次或多次。

进一步评论

要匹配多个序列，请添加g全局匹配修饰符。
以下$&在 a 上拆分每个匹配,并将结果推送到@matches。

my $str = "sdfds cat_dog,horse,rabbit,chicken-pig then some more pig,duck,goose";
my @matches;

while ($str =~ /[^,\s]+(,[^,\s]+)+/g) {
    push(@matches, split(/,/, $&));
}   

print join("\n",@matches),"\n";

score 1 · Accepted Answer

虽然你可能可以构造一个单一的正则表达式，一个正则表达式的组合，splits，grep看起来map不错

my @array = map { split /,/ } grep { !/^,/ && !/,$/ && /,/ } split

从右到左：

split在空格 ( )上分割线
只保留两端没有逗号但内部有一个逗号的元素 ( grep)
将每个这样的元素拆分为部分 (map和split)

这样，您可以轻松更改部分，例如消除两个连续的逗号添加&& !/,,/内部grep。

score 1 · Accepted Answer

我希望这很清楚并适合您的需求：

 #!/usr/bin/perl
    use warnings;
    use strict;

    my @strs = ("ewrfs sdfdsf cat_dog,horse,rabbit,chicken-pig",
    "fdsf iiukui aawwe dffg elephant,MOUSE_RAT,spider,lion-tiger hdsfds jdlkf sdf", 
     "dsadp poids pewqwe ANTELOPE-GIRAFFE,frOG,fish,crab,kangaROO-KOALA sdfdsf hkew", 
     "Saturn was long thought to be the only ringed planet, however, this is now known not to be the case.",
     "Another sentence, although having commas, should not confuse the regex with this: a,b,c,d");

    my $regex = qr/
                \s #From your examples, it seems as if every
                   #comma separated list is preceded by a space.
                (
                    (?:
                        [^,\s]+ #Now, not a comma or a space for the
                                 #terms of the list

                        ,        #followed by a comma
                    )+
                    [^,\s]+     #followed by one last term of the list
                )
                /x;

    my @matches = map {
                    $_ =~ /$regex/;
                    if ($1) {
                        my $comma_sep_list = $1;
                        [split ',', $comma_sep_list];
                    }
                    else {
                        []
                    }
                } @strs;

score 0 · Accepted Answer

$var =~ tr/ //s;    
while ($var =~ /(?<!, )\b[^, ]+(?=,\S)|(?<=,)[^, ]+(?=,)|(?<=\S,)[^, ]+\b(?! ,)/g) {
      push (@arr, $&);
    }

正则表达式匹配三种情况：

(?<!, )\b[^, ]+(?=,\S) : matches cat_dog
(?<=,)[^, ]+(?=,)      : matches horse & rabbit
(?<=\S,)[^, ]+\b(?! ,) : matches chicken-pig

regex - Perl - Regex to extract only the comma-separated strings

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