Example: updating an XML document

#!/bin/perl -w
use strict;
use XML::Parser;
my $RATE= 7.20;
my $in_price;
my $parser= new XML::Parser( Style => "Stream");
$parser->parsefile( "wine.xml");
sub StartTag
  { if( $_[1] eq "price")
      { $in_price= 1;
        # DANGEROUS!
        # print '<price currency="FF">';
        $_{currency}= 'FF';
        print join( ' ', "<$_[1]", map { "$_=\" " . $_{$_} . "\"";} keys %_)
              . ">"; 
      }
    else
      { print $_; }
  }
sub Text
  { if( $in_price)
      { $_ *= $RATE; $in_price= 0; } 
    print $_; 
  }