"'Not I,' said the sheep." I get impatient, so used 1s sleep, not 5s. But it works how I believe you intend for me using Strawberry v5.26.0.

use warnings;
use strict;
use Term::ReadKey;

ReadMode 4;
my $key;
while( !defined ($key = ReadKey(-1)) ) {
    print qq(Test\n);
    sleep(1);
}
print qq(Exit With Key $key\n);

__END__

From cmd.exe prompt:

C:\usr\local\share\PassThru\perl\perlmonks>perl 1212444.pl
Test
Test
Exit With Key a

C:\usr\local\share\PassThru\perl\perlmonks>perl -v

This is perl 5, version 26, subversion 0 (v5.26.0) built for MSWin32-x
+64-multi-thread
[download]

relevant update: windows 10, 1709 (os build 16299.248)

irrelevant update: whoops, there was no sheep, just a pig, cat, and rat... and it's actually "and the cat said, 'not I'". I guess it's been a few years since my kids last requested that story.