G'day Priti24,

This appears to do what you want:

$ perl -Mstrict -Mwarnings -E '
    use utf8;
    my $internal_string_2 = q{aÜaerzz};
    say for map { /[a-z0-9]/i
                    ? $_
                    : sprintf "\\U%04X" => unpack "W*", $_
    } chr(469), chr(471), chr(532), split // => $internal_string_2;
'
\U01D5
\U01D7
\U0214
a
\U00DC
a
e
r
z
z
[download]

For more information, take a look at perluniintro and specifically the example in Displaying Unicode As Text.