$var =~ s/$lhs/$rhs/ee; #### $var =~ s/$lhs/eval $rhs/e; #### $rhs = '"$1$2$3"'; #### $rhs = '$1.$2.$3';
## $var =~ s/$lhs/eval $rhs/e; ##
## $rhs = '"$1$2$3"'; ##
## $rhs = '$1.$2.$3';