Notes in Perl

Here are some notes for learning and using Perl. List one item today:

1. Analyze the Matching content of the following regular expression

/^/B [/W.] {1, 12}/B $/

 

Answer: This regular expression matches a line that starts with a character and ends with a length between 1 and 12 characters. The letters in the regular expression are common letters, numbers, or underscores.

Is it strange that the "." In the expression does not work?

Normally, when "." appears in the character set, it should match "." itself, rather than any character. But here the problem lies in the anchor points of/B, which indicates that they contain a word, here, only common letters, numbers, and underscores are supported, excluding ". ".