Finding a particular value in an HTTP response using Perl

Question

I have a little script in Perl, HTTP POST request

my $request =  $ua->post( $url, [ 'country' => 10, 'evalprice' => 0 ] );
my $response = $request->content;

Now I know that in the response there will be this part, which appears only once

:&nbsp;<b>9570&nbsp;USD

I want to take only the number 9570 (or whatever it will be), I don't know how to search for

:&nbsp;<b>

and then just take the part after that and before

 USD

I guess regular expressions will help, but I can't figure out how to use them here.

Answer 1

You were on the right track with the regular expression. You only need one expression, and since your string is straightforward, you don't even need a very complicated one.

my $content =~ m/:&nbsp;<b>([.\d]+)&nbsp;USD/;
my $price = $1;

The m// is the matching operator. Together wil =~ it tells Perl to do a regular expression to your variable $content . We have a capture group ( () ) that contains the price, and it's contents will go into $1 . The [.\\d+] is a group of characters. The dot is just a dot (your price might have cents), and the \\d means all digits ( 0 - 9 ). The + says there may be lots of these characters, but at least one.

• Try it out at http://rubular.com
• Read more on Regular Expressions in perlre and perlretut
• Have a look at WWW::Mechanize if you want to do more to the website

Answer 2

Use code like this (removing HTML entities is nice, but optional):

use HTML::Entities;

my $content = ":&nbsp;<b>9570&nbsp;USD";
my $decoded = decode_entities($content); # replace &nbsp; to spaces
my ($price) = ($decoded =~ /<b>(\d+)\s*USD/);
print "price = $price\n";

Answer 3

The safest way to parse HTML is with the help of a proper CPAN module. But a simple alternative (if the response is simple) may be this;

use strict;
use warnings;

my $str = ":&nbsp;<b>9570&nbsp;USD";

if( $str =~ m/:&nbsp;<b>(\d+)&nbsp;/ ) {
   print $1, "\n";
}

I have used a regular expression, and the number is at $1 when a match is found.