单词边界: \b匹配单词边界,就是位于单词(\w)和非单词字符(\W)之间的零宽度的地方。 就是单词前后必须跟非单词字符 [oracle@jhoa big]$ cat 11.pl #$var = "The Great Fred"; $var = "Fred erick the Great"; if ($var =~/\bFred\b/){print "$var\n"}; [oracle@jhoa big]$ perl 11.pl Fred erick the Great [oracle@jhoa big]$ cat 11.pl #$var = "The Great Fred"; $var = "aFred erick the Great"; if ($var =~/\bFred\b/){print "$var\n"}; [oracle@jhoa big]$ perl 11.pl [oracle@jhoa big]$ Fred前面出现单词字符,匹配不上 [oracle@jhoa big]$ cat 11.pl #$var = "The Great Fred"; $var = "Freda erick the Great"; if ($var =~/\bFred\b/){print "$var\n"}; [oracle@jhoa big]$ perl 11.pl [oracle@jhoa big]$ Fred后面出现单词字符匹配不上 [oracle@jhoa big]$ cat 11.pl #$var = "The Great Fred"; $var = "!Fred erick the Great"; if ($var =~/\bFred\b/){print "$var\n"}; [oracle@jhoa big]$ perl 11.pl !Fred erick the Great [oracle@jhoa big]$ 单词前面出现非单词字符,可以匹配 [oracle@jhoa big]$ cat 11.pl #$var = "The Great Fred"; $var = "Fred! erick the Great"; if ($var =~/\bFred\b/){print "$var\n"}; [oracle@jhoa big]$ perl 11.pl Fred! erick the Great [oracle@jhoa big]$ 单词后面出现非单词字符,可以匹配
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