Perl正则表达式在模式匹配之前全局插入换行符

Question

I am struggling to insert a newline before a matching string that consists of a period followed by 2 or 3 characters (alphanumeric) and ending with another period. If possible, this needs to be a single statement that acts upon an entire file.

Something like (?):

$contents =~ s/\.{2,3}\./\n\.<what goes here?>\./g;

Specifically, I am dealing with a file of many catalog records in a 2-step process. Step 1: removing all carriage returns from the file. Step 2: finding text strings such as .AUTH. and .RE. and even .856. and making each of these the beginning of a new line. I can do this with a long series of specific substitutions,

$contents=~s/\.RE\./\n\.RE\./g;
$contents=~s/\.AUTH\./\n\.AUTH\./g;
$contents=~s/\.TITL\./\n\.TITL\./g;

But my understanding is that I can also do this more efficiently with a single statement (using regex built-in variables?)

Thanks,

Thom

Answer 1

To remove all new-line characters use

$contents =~ s/\n//g;

To add desired new-line characters use

$contents =~ s/(?=[.][a-z\d]{2,3}[.])/\n/ig;

Answer 2

$contents =~ s/(\.\w{2,3}\.)/\n$1/;

使用括号记住匹配的字符串，并在替换部分使用$ 1引用它。