To make it generic you would need a capture group. eg:

Is this what you were after?

Update: for an example with more obvious genericism try:

Or as a simplification, s/(na$)/\U$1/ or just s/na$/NA/

Perl 6 - the future is here, just unevenly distributed

G'day sumandas,

Please do not delete your post and just replace it with something different.

Three monks have voluntarily given their time to try to help you. Because you've changed your post, their responses are meaningless and you have completely wasted their time!

Please read "How do I change/delete my post?".

Given your new question, this does what you ask:

#!/usr/bin/env perl -l

use strict;
use warnings;

my @strings = qw{MUXmh123 MUXho124 999999};

my @results = map { /(\D+)/ ? "\U$1-" : () } @strings;

print for @results;
[download]

Output:

MUXMH-
MUXHO-
[download]

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.