#!/usr/bin/perl
 
$txt="1234ab56";
$txt =~ /\d\d/g;
print "matched $&: ",pos $txt,"\n";
$txt =~ /\d\d/g;
print "matched $&: ",pos $txt,"\n";
$txt =~ /\G\d/g;     # 强制从位移4开始匹配，无法匹配字母a，但又不允许跳过
                     # 所以本次\G全局匹配失败，由于没有修饰符c，指针重置
print "matched $&: ",pos $txt,"\n";
$txt =~ /\G\d/g;     # 指针回到0，强制从0处开始匹配，数值1能匹配成功
print "matched $&: ",pos $txt,"\n";