That should be local our $check;. Let's not clobber our caller's variables. 

sub getChecksum($) {
        my $in = shift;
        local our $check = 0;
        $in =~ m/(?:(.)(?{$check += ord($1);}))*^/;
        return $check;

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In reply to Re^2: Weird behaviour with match-time code evaluation and backtracking by ikegami
in thread Weird behaviour with match-time code evaluation and backtracking by moensch

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