I often use a solution more or less like this, that is based on a hash where the key is the value to be sorted (and in this case is case-insensitive) and the value is the actual string to be printed. It's quite compact and it kills dupes for free. As in this case I don't want it to kill dupes, I append an unique counter to the key so that each key is guaranteed to be unique.

Here's the code: 

use strict;
my %hDat;
my $d; 
my $n;

map( ($hDat{lc $_ . $n++} = $_), <DATA> );
foreach $d (sort keys %hDat) { print $hDat{$d}; }

__DATA__
a
B
c
D
E
Aa
Xx
A

[download]
And here's the result: 
a
A
Aa
B
c
D
E
Xx
You know, there is more than one way. :-)

In reply to Using a hash by l3nz
in thread noncase-sensitive sorting by texuser74

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