If each cleanup action is different, consider putting that code in a subroutine to simplify the while loop. For example

#!perl
use strict;

my %mycorpus = (
  a => "date:#20180101# title:#cat dog# text:#sheep sheep sheep sheep#
+" ,
  b => "date:#20180101# comment:#woof woof#",
  c => "date:#20180101# title:#cow puppy# text:#pig pig pig#",
);

my %counts;
foreach my $filename (sort keys %mycorpus) {
  my $date;

  if ($mycorpus{$filename} =~ /date:#(\d{8})#/g){ 
    $date = $1;  
  } else {
    die "No date found filename : $filename => $mycorpus{$filename}";
  }
  
  while ($mycorpus{$filename} =~ /(title|text|comment):#(.*?)#/g){
    my $dataset = cleanup($1,$2);
    my @words = split /\W+/, $dataset;

    foreach my $word (@words){

      if ($word =~ /(\w+)/gi){
        $word =~ tr/A-Z/a-z/;
        $counts{$date}{$word}++;
       #$word_types{$word}++;
       #$overallcounts{$date}++;
      }
    }   
  }  
}

sub cleanup {
  my ($key,$value) = @_;
  if ($key eq 'title'){
     #Actions usually performed here which clean the titles 
     #(i.e. substituting certain characters)
  }
  if ($key eq 'text'){
     #Actions usually performed here which clean the text 
  }
  if ($key eq 'comment'){
     #Actions usually performed here which clean the comments 
  }
  return $value;
}

use Data::Dumper;
print Dumper \%counts;
[download]

poj

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.