zentara,
It appears you have a typo in that there is an overlap with 'r'..'z' and 'a'..'s' but it shouldn't cause a problem. Personally, I would steal a page from broquaint's bag of tricks:

#!/usr/bin/perl
use strict;
use warnings;

my @unsorted = ( qw (Psdf lPik Easd aKwe SSdf eqwer scfgh Oegb rqwer T
+) );
my %order = map {$_ => /[r-z]/ ? 'A' : /[a-q]/ ? 'B' : /[R-Z]/ ? 'C' :
+ 'D'} ('a'..'z', 'A'..'Z');

my @sorted = map { substr($_ , 1) }
             sort
             map { $order{ substr($_,0,1) } . $_ } @unsorted;

print "$_\n" for @sorted;
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Cheers - L~R