用正则表达式处理文本

1.用s///替换
[root@oa1 home]# cat test1 
#!/usr/bin/perl
$_ = "He's out bowling with Barney tonight.";
s/Barney/Fred/;
print "$_\n";
[root@oa1 home]# ./test1 
He's out bowling with Fred tonight.


2.用$1替换变量
[root@oa1 home]# cat test2 
#!/usr/bin/perl
$_ = "He's out bowling with Barney tonight.";
s/with (\w+)/against $1's team/;
print "$_\n";
[root@oa1 home]# ./test2 
He's out bowling against Barney's team tonight.

3.
$_ = "greem scaly dinosaur";
s/(\w+) (\w+) /$2, $1/;   #替换后为"scaly, green dinosaur"
s/^/huge, /;                   #替换后为"huge, scaly,green dinosaur"
s/,.*een//;                     #空替换，此时为"huge dinosaur"
s/green/red/;                 #匹配失败：仍为"huge dinosaur"
s/\w+$/($`!)$&/;           #替换后为 "huge (huge!) dinosaur"
s/s+(!\W+)/$1 /;            #替换后为"huge (huge!) dinosaur"
s/huge/gigantic/;            #替换后为"gigantic (huge!) dinosaur"

$_ = "fred filintstone";
if (s/fred/willma){
    print "Successfully replaced fred with wilma!\n";
}