Hi sumandas,

In your code you no need to use $str =~ m/na/you can directly use the $str =~ s/na//gi; code, as you need to check the "na" string to be matched at the end of the srtring, perl has the special chater "$" used to match at the end of the sctring, so $str =~ s/na$//gi; this will match the "na" at the end of the string, now u want that "na" at the end of the string to be converted to UPPERCASE "na", so we need to get the same substring to replace, so we need to group it, as $str =~ s/(na)$/uc($1)//gi;, the grouped string will be available in $1 special variable, and use the uc() BIF to convert the matched substring to uppercase.