#!/usr/bin/perl 

$name="123ab456";
$name =~ m/\d\d/g;     # 第一次匹配，匹配成功后记下位移
print "matched string: $&, position: ",pos $name,"\n";
$name =~ m/\d\d/g;     # 第二次匹配，匹配成功后记下位移
print "matched string: $&, position: ",pos $name,"\n";

# 匹配失败的时候，正则匹配操作会返回假，所以可以作为if或while等的条件语句
$name="123ab456";
while($name =~ m/\d\d/g){
    print "matched string: $&, position: ",pos $name,"\n";
}