I found it. man perlop for backticks: "In scalar context, a single string consisting of all output is returned. In list context, a list of values is returned, one per line of output." Solution: 
print escapeHTML(scalar(`echo abc; echo def; echo ghi`));

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In reply to Re: backticks/escapeHTML strange behaviour with assignment by candlerb
in thread backticks/escapeHTML strange behaviour with assignment by candlerb

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