This may work better (UNTESTED): 

#!/usr/bin/perl

use strict;
use warnings;


my @allTags;

{   local @ARGV = <[0-9][0-9][0-9][0-9].txt>;

    my %uniqueTags;
    while ( my $line = <> ) {
        next unless $line =~ s/^tags\s+//;
        $line =~ s/\s+\z//;
        $uniqueTags{ $_ } = 1 for split /\s+,\s+/, $line;
        }

    @allTags = keys %uniqueTags;
    }

print "@allTags\n";

[download]

In reply to Re: Mapping list to hash is dropping list items by jwkrahn
in thread Mapping list to hash is dropping list items by almsdealer

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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