We're migrating some legacy flat files to databases. The structure of the flat files is like that in the __DATA__ block shown below. Tags are short upper case strings followed by equal-sign and white space. Data fields are mostly unstructured text (we have verified that upper case TAGn strings never occur in the data). I want to capture both the tags and the data to build hashes.

Ideally, I want to use method 1 and create the regex on the fly from tags read from other files. As you can see, my attempt fails miserably (does not split where I want to split).

So I tried method 2 and made the regex manually. That one almost works, except that I end up with an extra (empty) value in $stuff2[0], which makes a subsequent %hash = @stuff2 break.

OK, the input is not that ugly, but I thought the solution would be easier. What am I missing? 

use 5.010;
use strict;
use warnings;

$/ = undef;
my $data = <DATA>;

#method 1: build regex on the fly (read tags from files)
say '---------- method 1 ----------';
my @tags = qw(
                 TAG1
                 TAG2
                 TAG3
                 TAG4
            );

my $tags_re = join "|", @tags;
$tags_re = qr{ $tags_re };
say $tags_re;

my @stuff = split /($tags_re)=\s*/, $data;
say "#$_#"      for @stuff;

# method 2: static regex
say '---------- method 2 ----------';
my @stuff2 = split /(TAG1|TAG2|TAG2|TAG4)=\s*/, $data;
say "#$_#"      for @stuff2;

__DATA__
TAG1= data
TAG2= more data
TAG3= even more data that sometimes has = and
runs on to more
than one line
TAG4= still more

[download]
OUTPUT: 
---------- method 1 ----------
(?-xism: TAG1|TAG2|TAG3|TAG4 )
#TAG1= data
#
#TAG2#
#more data
#
#TAG3#
#even more data that sometimes has = and
runs on to more
than one line
TAG4= still more
#
---------- method 2 ----------
##
#TAG1#
#data
#
#TAG2#
#more data
TAG3= even more data that sometimes has = and
runs on to more
than one line
#
#TAG4#
#still more
#

[download]

In reply to problems splitting ugly input data by Anonymous Monk

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