使用perl編輯文件

Question

我有一個很大的文件（有超過20,000行），其中一些行正在用「+」盯着。它的形式如下：

This is a file with many lines 
Some lines start with plus 
+ line one 
+ line two 
Some lines do 
not start with plus 
+ line three 
+ line four 

我想加入所有以+開頭的行和前一行。所以我的輸出應該是這樣的：

This is a file with many lines 
Some lines start with plus line one line two 
Some lines do 
not start with plus line three line four 

我該怎麼用perl做這個？

Answer 1

就地文件編輯，

perl -i -pe 'BEGIN{ $/ ="\n+" } chomp' file