第八章： 以正则表达式进行匹配

#! /usr/bin/perl
use strict;
use warnings;

#my @strict_pragma = qw ( a b c);
#print $strict_pragma[0];

print " ----------------------------------_delimiter_match_http://-------------------------- ";
$_ = "https://www.cnblogs.com/books2read/";
if(m%http[s]*://%){
    print "unpacking_@_ * 1 ";
}
print " ----------------------------------_delimiter_match_http://-------------------------- ";

print " ----------------------------------_optional_modifiers_---------------------------------------------------------------------------------------------- ";
print "unnecessary subscripting:";
chomp($_ = <STDIN>);
if(/yes/i){
    print "array-ref values. "
}
print " ----------------------------------_/s-------------------------- ";
$_ = " naming conventions references to slice factoring slicing anonymous attribute demolition.";
if(/conventions.*demolition/s){
    print "string mentions demolition after conventions. ";
}
print " ----------------------------------_/s-------------------------- ";
print " ----------------------------------_optional_modifiers_---------------------------------------------------------------------------------------------- ";

print " ----------------------------------_/x-------------------------- ";
$_ = "demolition array-ref values.  2";
if(/
    -?  # one optional minus sign
    d+ # one or more digits before the decimal point
    .? # an optional decimal point
    d* # some optional digits after the decimal point
/x){
    print "match *1. "
}
$_ = "3415";
if(/
    -?  # one optional minus sign
    d+ # one or more digits before the decimal point
    .? # an optional decimal point
    d* # some optional digits after the decimal point
/x){
    print "match *2. "
}
print " ----------------------------------_/x-------------------------- ";

print " ----------------------------------_combining_opiton_modfiers-------------------------- ";
$_ = " naming conventions references to slice factoring slicing anonymous attribute Demolition.";
if(/conventions.*demolition/si){
    print "string mentions demolition after conventions. match*3 ";
}
print " ----------------------------------_combining_opiton_modfiers-------------------------- ";

print " ----------------------------------2222_combining_opiton_modfiers-------------------------- ";
$_ = " naming conventions references to slice factoring slicing anonymous attribute Demolition.";
if(/
    conventions
    .*
    demolition
    /six){
    print "string mentions demolition after conventions. match*4 ";
}
print " ----------------------------------222_combining_opiton_modfiers-------------------------- ";

print " ----------------------------------_anchors_-------------------------- ";
$_ = "ATTR marker,";
my $contextual;
if(/s+(w+),/){
    print "Caret anchor works. ";
    $contextual = $1;
}
print " ----------------------------------_anchors_-------------------------- ";

print " ----------------------------------_persistence_of_memory-------------------------- ";
my $precedence = "!!!";
$precedence =~ /(w+)/;
print "precedence's word was $1 ... or was it? ";
# to prevent the matching variable override, you can store it in a defined variable
print $contextual;
print " ----------------------------------_persistence_of_memory-------------------------- ";

print " ----------------------------------_automatic_match_variable-------------------------- ";
$_ = "ATTR marker,";
if(/s+(w+),/){
    print "That actually matched '$&'. ";
}
print "That was ($`)($&)($'). ";
print ($`);
print " ";
print '$&'." ";
print $'." ";
print " ";
print '$contextual';
print " ";
print $contextual;
print " ----------------------------------_automatic_match_variable-------------------------- ";

print " ----------------------------------_general_quantifiers-------------------------- ";
$_ = ",,,,,,";
if(/,{5}/){
    print "match * 8 ";
}
print " ----------------------------------_general_quantifiers-------------------------- ";

print " ----------------------------------_pattern_test_program-------------------------- ";
$_ = "test, it's!";
if(/w+,s+w+'/){
    print "matched: <$`><$&><$'>| ";
}
print " ----------------------------------_pattern_test_program-------------------------- ";

print " ----------------------------------_ch8_Q1-------------------------- ";
$_ = "beforematchafter";
if(/match/){
    print "matched: <$`><$&><$'>| ";
}
print " ----------------------------------_ch8_Q1-------------------------- ";

print " ----------------------------------_ch8_Q2-------------------------- ";
$_ = "beforematcha? fter";
if(/w+a/){
    print "matched: <$`><$&><$'>| ";
}
print " ----------------------------------_ch8_Q2-------------------------- ";