You can use !~ instead of =~. So, $string !~ "hello" would return true if the string doesn't contain "hello". See perlop (perldoc perlop) for more information on operators.

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print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
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