This is a nice trick, but I guess it will have to search through the entire line, not only the beginning, so it can be a bit slow.

Possibbilities are:

my @new = grep { rindex $_, 'QKC_', 0 } @orig;
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or simply

my @new = grep { substr($_, 0, 4) ne 'QKC_' } @orig;
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