my $str = "Foooboooobaaar";

while($str =~ /(\w)(\1+)/gi)
{
print "\nInside while concat_str -- $1 ---- $2 ---> $1.$2";
$str_concat = $1.$2;
$str_rep_concat = $1.'*';
$str=~ s/$str_concat/$str_rep_concat/gi;
}
print "\n$str";