$_=<<'E';chop;
GGxGGGGaGGGGbGG/
0/1//
1/2/ab0
E
while(1){if(s!^GG((?:[^/\\]|\\.)*?)GG!!s){my
$s=$1;$s=~s/\\(.)/$1/gs;$d=getc();while(s/(?:\Q$s\E)/$d/){}}elsif(s!^([^/\\][^/\\G]*)!! or s!^\\(.)!!s){print($1);}elsif(s!^/((?:[^/\\]|\\.)*)/((?:[^/\\]|\\.)*)/!!s){my($s,$d)=($1,$2);$s=~s/\\(.)/$1/gs;$d=~s/\\(.)/$1/gs;while(s/(?:\Q$s\E)/$d/){}}else{last;}}