Found it! The file is binary, so there are binary zero bytes behind the texts when I extract these. I did not think about that and used

(@c) = $block =~ /(\d{14})(\d\d)(.*)/;
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to extract the contents. Thus the zero bytes were kept as part of $c3. Instead I should have used

(@c) = $block =~ /(\d{14})(\d\d)([ -z]*)/;
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This now yields

Two names: 'F#maj13/Eb      ', 'Gbmaj13/Eb      ' for         D#/Eb4, 
+F#/Gb4, A#/Bb4, F5,
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as I intended it. Thank any way for your help, it pushed me in the right direction!