Perl如何为正则表达式匹配结果分配变量

Question

How do you create a $scalar from the result of a regex match? Is there any way that once the script has matched the regex that it can be assigned to a variable so it can be used later on, outside of the block. IE. If $regex_result = blah blah then do something. I understand that I should make the regex as non-greedy as possible.

#!/usr/bin/perl
use strict;
use warnings;
# use diagnostics;
use Win32::OLE;
use Win32::OLE::Const 'Microsoft Outlook';
my @Qmail;

my $regex = "^\\s\*owner \#";
my $sentence = $regex =~ "/^\\s\*owner \#/";

my $outlook = Win32::OLE->new('Outlook.Application')
    or warn "Failed Opening Outlook.";
my $namespace = $outlook->GetNamespace("MAPI");
my $folder    = $namespace->Folders("test")->Folders("Inbox");
my $items     = $folder->Items;

foreach my $msg ( $items->in ) {
    if ( $msg->{Subject} =~ m/^(.*test alert) / ) {
        my $name = $1;
        print "  processing Email for $name \n";
        push @Qmail, $msg->{Body};
    }
}

for(@Qmail) {
  next unless /$regex|^\s*description/i;
  print; # prints what i want ie lines that start with owner and description
}

print $sentence; # prints ^\\s\*offense \ # not lines that start with owner.

Answer 1

One way is to verify a match occurred.

use strict;
use warnings;

my $str = "hello what world";

my $match  = 'no match found';
my $what  = 'no what found';
if ( $str =~ /hello (what) world/ )
{
   $match = $&;
   $what = $1;
}

print '$match = ', $match, "\n";
print '$what = ', $what, "\n";

Answer 2

The match of a regex is stored in special variables (as well as some more readable variables if you specify the regex to do so and use the /p flag).

For the whole last match you're looking at the $MATCH (or $& for short) variable. This is covered in the manual page perlvar .

So say you wanted to store your last for loop's matches in an array called @matches , you could write the loop (and for some reason I think you meant it to be a foreach loop) as:

my @matches = ();
foreach (@Qmail) {
    next unless /$regex|^\s*description/i;
    push @matches_in_qmail $MATCH
    print;
}

I think you have a problem in your code. I'm not sure of the original intention but looking at these lines:

my $regex = "^\\s\*owner \#";
my $sentence = $regex =~ "/^\s*owner #/";

I'll step through that as:

• Assign $regex to the string ^\\s*owner # .
• Assign $sentence to value of running a match within $regex with the regular expression /^s*owner $/ (which won't match, if it did $sentence will be 1 but since it didn't it's false).

I think. I'm actually not exactly certain what that line will do or was meant to do.

Answer 3

I'm not quite sure what part of the match you want: the captures, or something else. I've written Regexp::Result which you can use to grab all the captures etc. on a successful match, and Regexp::Flow to grab multiple results (including success statuses). If you just want numbered captures, you can also use Data::Munge

Answer 4

You can do the following:

my $str ="hello world";  
my ($hello, $world) = $str =~ /(hello)|(what)/; 

say "[$_]" for($hello,$world);

As you see $hello contains "hello".

Answer 5

Use Below Perl variables to meet your requirements -

$` = The string preceding whatever was matched by the last pattern match, not counting patterns matched in nested blocks that have been exited already.

$& = Contains the string matched by the last pattern match

$' = The string following whatever was matched by the last pattern match, not counting patterns matched in nested blockes that have been exited already. For example:

$_ = 'abcdefghi';
/def/; 
print "$`:$&:$'\n";    # prints abc:def:ghi

Answer 6

If you have older perl on your system like me, perl 5.18 or earlier, and you use $ $& $' like codequestor's answer above, it will slow down your program.

Instead, you can use your regex pattern with the modifier /p , and then check these 3 variables: ${^PREMATCH} , ${^MATCH} , and ${^POSTMATCH} for your matching results.