while (<OUTFILE>) {
    chomp;                              # <== move the chomp here
    my ($key, $value) = split /;/;
    $calhash{$key} = $value;            # not '= $key'
}

##</code><code>##

foreach my $key (sort {$b cmp $a} keys %calhash) {
    my $value = $calhash{$key};
    print TESTFILE "$key;$value\n";
}