I built this test script around your code:

#!/usr/local/bin/perl -w

use strict;

my @database = <DATA>;

my @sorted=sort{my $one=substr($a,rindex($a,'|'));
                my $two=substr($b,rindex($b,'|'));
                ($one <=> $two) } @database;


print @sorted;

__DATA__
a|b|c|10
d|e|f|100
g|h|i|2
[download]

which produced the following output:

Argument "|10\n" isn't numeric in ncmp at tmp.pl line 9, <DATA> chunk 
+3.
Argument "|100\n" isn't numeric in ncmp at tmp.pl line 9, <DATA> chunk
+ 3.
Argument "|100\n" isn't numeric in ncmp at tmp.pl line 9, <DATA> chunk
+ 3.
Argument "|2\n" isn't numeric in ncmp at tmp.pl line 9, <DATA> chunk 3
+.
a|b|c|10
d|e|f|100
g|h|i|2
[download]

The warnings reveal the problem quite conveniently; the substr() is including the pipe character, so all the values being compared are numerically equal to zero and thus to each other.

You can easily fix this error by adding 1 to each rindex(). However, I would suggest making another change as well. You're doing a fair amount of work in the sort subroutine, which makes it inefficient. A Schwartzian Transform moves the work out of the sort sub:

my @sorted = map $_->[1],
             sort { $a->[0] <=> $b->[0] }
             map [ substr($_,rindex($_,'|')+1), $_ ],
             @database;
[download]

But, there's another option that would work well here, and should be even more efficient because it uses an optimized sort sub. This one is often called the Guttman-Rosler Transform:

my $width = 10;  # must be at least as big as the longest field being 
+compared
my @sorted = map substr($_, index($_, '|')+1),
             sort
             map sprintf("%0${width}d|%s", substr($_,rindex($_,'|')+1)
+, $_),
             @database;
[download]

As you can see, this is very similar to the Schwartzian Transform, but the intermediate value is a string instead of an anonymous array.

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