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my @find = $line[$i] =~ /\tabc\d\t/g
my @find = $line[$i] =~ /\tabc\d+\t/g
my @find = $line[$i] =~ /(?:\A|\t)abc\d+(?:\t|\z)/g
my @find = $line[$i] =~ /(?:\A|\t)(abc\d+)(?=\t|\z)/g