@seq = ('acgt','actg','cggt','cggt', 'actg', 'actg'); @num = ('1234','2345','3244','3455', '5230', '100000' ); for( 0..$#seq ){ $struct{$seq[$_]}->[0] += $num[$_] and $struct{$seq[$_]}->[1]++ } for( keys %struct ){ print "$_\t", $struct{$_}->[0] / $struct{$_}->[1], $/ } __END__ STDOUT: acgt 1234 cggt 3349.5 actg 35858.3333333333