Wise monks:

While working on a quick script to parse some files for our site, I came across something peculiar.

In the code below, I'm setting my hash %date to '' in each of the three elements: YEAR, MONTH, and DATE. I then use embedded code in a regular expression to populate those fields.

On the first pass, everything comes out as expected, i.e. %date is populated correctly. But on every subsequent pass, %date is populated inside of the regular expression (as demonstrated), but upon leaving the regular expression, it seems to clear itself.

When the @file_names are rearranged, there is no different effect. It still works on the first iteration, and the remaining two do not. Any thoughts? I'm sure I'm overlooking something. 

use strict;
use warnings;

use Data::Dumper;

my @file_names = qw(
   /a/990101ag/toc.html
   /a/20000115/toc.html
   /a/990115ag/toc.html
);

for my $file_name ( @file_names ) {
   print "Now working on $file_name\n";

   my %date = ( YEAR => '', MONTH => '', DAY => '' );
   $file_name =~ m#
      (?<=/a/)
      (\d{2,4})(\d{2})(\d{2})(?:ag)?
      (?=/)
      (?{ @date{'YEAR', 'MONTH', 'DAY'} = ( (
         length($1) == 2
         ? '19' . $1
         : $1), $2, $3
       ) })
      (?{ print "Here, \%date is populated (joined): ", 
                join('-', @date{'YEAR', 'MONTH', 'DAY'}),
                "\n"
       })
   #x;

   print "But after the first iteration, ",
         "it isn't populated here (joined): ",
         join('-', @date{'YEAR', 'MONTH', 'DAY'}),
         "\n";
   print Dumper(\%date);

   print "\n\n";
}

print "Why????\n";

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In reply to regex code embedding problem? by perlguy

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