#!perl
$_="@ARGV
";print($y=$5||$1||$&),s/$y//gwhile/(.)(.)(.).*(\2\1|\1(\2)(?!.*\3))|.
/

#!perl
$_="@ARGV
";print($y=$5||$6),s/$y//g while/(.)(.)(.).*(\1(\2)(?!.*\3)|\2(\1))/;print substr$_,2