Hello perl guru, I have a question on sorting. Browsing through the internet as well as here, I came across some code snippets on sorting. Finally, I did this (example from Tom C.) from his "FMTEYEWTK": 
--
#!/usr/bin/perl
my $str = `type unsort.txt`;

$str = join("\n", 
        map($_->[0],
            sort( {$a->[0] cmp $b->[0] }
              map( [$_, (split('|', $_))[-1] ], 
                   split(/\n/, $str)
                 )
             )
           )
           );

print $str;
--

[download]
unsort.txt contains the following: 
--
xyz4|1026|CR
xyz3|3461|CR
dert5|3251|PR
rtyaq|251|PR
dbca|583|PR
xxxt|360|CR
--

[download]
Output is the following which is correct: 
dbca|583|PR
dert5|3251|PR
rtyaq|251|PR
xxxt|360|CR
xyz3|3461|CR
xyz4|1026|CR

[download]
But if I change the sort fn to 
sort( {$a->[1] cmp $b->[1] }

[download]
which I am sorting the list using the first field as the key, then I got the following output: 
--
xyz4|1026|CR
xyz3|3461|CR
dert5|3251|PR
rtyaq|251|PR
dbca|583|PR
xxxt|360|CR
--

[download]
1. The above is not sorted at all. What did I do wrong?
2. What if I want to sort using field 1 and field 2 as keys. What do I have to do? I have been trying to find answers from the WWW but to no avail.
I appreaciate your help. TIA. Vincent

In reply to sorting question by chanv

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