$bit = substr((split($data,"\Q$sequence\E"))[1],0,$length);
($bit) = $data =~ /sequence(.{$length})/;
$bit = subst($data,index("$sequence") + length("$sequence"),$length)
$bit = "$data"; $bit =~ s/.*sequence//; $bit =~ s/(.{$length}).*/$1/;
/sequence/; $bit = substr($',0,$length);