use warnings;
use strict;
use File::Find;

my @name;
my $filename;
my $line;
my @severity = ();
my @files;
my @info = ();
my $key;
my %hoa;
my $xmlfile;
my $comment;
my @comments;

open( OUTPUT, "> $ARGV[0]" );
my $dir = 'c:/programs/TEST/Test';

while ( defined( $input = glob( $dir . "\*.txt" ) ) ) {
    open( INPUT, "< $input" );

    while (<INPUT>) {
        chomp;

        if (/File/) {
            my @line = split /:/;
            $key = $line[1];
            push @{ $hoa{$key} }, "Filenamen";
        }

        if ( /XML/ ... /File/ ) {
            $xmlfile = $1;
            push @{ $hoa{$key} }, "XML file is $xmlfilen";

        }
        if (/Important/) {
            push @{ $hoa{$key} }, "Severity is $_n";
        }
        if (/^D/) {
            next if /Important/;
            push @{ $hoa{$key} }, "Given comment is $_n";
        }
        push @{ $hoa{$key} }, "this stringn";
    }

}

foreach my $k ( keys %hoa ) {
    my @list = @{ $hoa{$k} };
    foreach my $l (@list) {
        print OUTPUT $l, "n";
    }
}

}
close INPUT;
close OUTPUT;

use strict;
use warnings;

use File::Find;

my ($outfile) = @ARGV;

my $dir = 'c:/programs/TEST/Test';

my %hoa;
my $key;

while (my $input = glob "$dir/*.txt") {

  open my $in, '<', $input or die $!;

  while (<$in>) {

    chomp;

    if (/File/) {
      my $key = (split /:/)[1];
      push @{ $hoa{$key} }, "Filenamen";
    }

    if (/XML/ ... /File/) {
      my $xmlfile = $1;
      push @{ $hoa{$key} }, "XML file is $xmlfilen";
    }

    if (/Important/) {
      push @{ $hoa{$key} }, "Severity is $_n";
    }

    if (/^D/) {
      next if /Important/;
      push @{ $hoa{$key} }, "Given comment is $_n";
    }

    push @{ $hoa{$key} }, "this stringn";
  }

  close $in;
}

open my $out, '>', $outfile or die $!;

foreach my $k (keys %hoa) {
  foreach my $l (@{ $hoa{$k} }) {
    print $out $l, "n";
  }
}

close $out;

for (values(%hoa)) { push @{$_}, "this string"; }

my %autoviv = ( a => ['foo'], b => undef );
push @$_, "PUSH" for values %autoviv;        # ( a => ['foo', 'PUSH'], b => ['PUSH'] )

my %fatal = ( a => {} );
push @$_, "PUSH" for values %fatal;          # FATAL:  "Not an ARRAY reference at..."

my %dangerous = (a => "foo");
push @$_, "PUSH" for values %dangerous;      # Yikes!  @foo is now ("PUSH")

use strict;
my %kablam = (a => "foo");
push @$_, "PUSH" for values %kablam;         # "Can't use string ("foo") as an ARRAY ref ..."

#!/usr/bin/perl

use warnings;
use strict;
use Data::Dumper;

my %hash = qw|
    key1    value1
    key2    value2
    key3    value3
|;

my %hash = map { $_ . "this string" => $hash{ $_ } } keys %hash;

print Dump %hash;

perl script.pl

$VAR1 = {
          'key3this string' => 'value3',
          'key2this string' => 'value2',
          'key1this string' => 'value1'
        };