require 5.010; #<- from your previous post
use strict;
use warnings;

# meth 1 of ?

my $x = 'a:b';
my @x = split(/:/,$x);
my $y = join(q{//}, @x);
print qq{$y\n};

# meth 2 of ?

my @z = sort{ $a <=> $b} @x;
my $a = join(q{//}, @z);
print qq{$a\n};

##</code><code>##

a//b
a//b