I've rewritten this script dozens of times, but I can't seem to spot my mistake

There's no SSCCE in there. Creating one shows the mistake quite clearly:

use strict;
use warnings;
use Test::More tests => 2;

my %mycorpus = (
    a => "<time datetime=2017-09-03T23:17:53Z>
blah
blah
##soft and softly is as softly does##
bar",
    b => "<time datetime=2017-09-03T23:17:53Z>
blah
blah
##Not so SOFT now, eh?##
foo",
    c => "<time datetime=2017-09-04T23:17:53Z>
blah
##Mr. Soft in the soft-play area##
baz"
);

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

        if ($mycorpus{$filename} =~ /(?<==)(\d{4}-\d{2}-\d{2})(?=T)/g)
+{
            $date = $1;
        }

        if ($mycorpus{$filename} =~ /(?<=##)(.*)(?=##)/g){
            $hashtags = $1;
        }

         if ($hashtags =~ /\bsoft/gi){
             $counts{$date}++;
         }
}

is ($counts{'2017-09-03'}, 4, "2017-09-03 tally correct");
is ($counts{'2017-09-04'}, 2, "2017-09-04 tally correct");

[download]

Your assignment to $counts{$date} is wrong - it only adds one count irrespective of how many matches there are in that line/file. Here's the fixed version:

use strict;
use warnings;
use Test::More tests => 2;

my %mycorpus = (
    a => "<time datetime=2017-09-03T23:17:53Z>
blah
blah
##soft and softly is as softly does##
bar",
    b => "<time datetime=2017-09-03T23:17:53Z>
blah
blah
##Not so SOFT now, eh?##
foo",
    c => "<time datetime=2017-09-04T23:17:53Z>
blah
##Mr. Soft in the soft-play area##
baz"
);

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

        if ($mycorpus{$filename} =~ /(?<==)(\d{4}-\d{2}-\d{2})(?=T)/g)
+{
            $date = $1;
        }

        if ($mycorpus{$filename} =~ /(?<=##)(.*)(?=##)/g){
            $hashtags = $1;
        }

         if (my $matches =()= $hashtags =~ /\bsoft/gi){
             $counts{$date} += $matches;
         }
}

is ($counts{'2017-09-03'}, 4, "2017-09-03 tally correct");
is ($counts{'2017-09-04'}, 2, "2017-09-04 tally correct");

[download]

In reply to Re: Counting instances of a string in certain sections of files within a hash by hippo
in thread Counting instances of a string in certain sections of files within a hash by Maire

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