First of all, those are colons, not semicolons. ;-) Sounds like a good place for a Schwartzian Transform by our own merlyn:

#!/usr/bin/perl

use strict;
use warnings;

my @data = <DATA>;
chomp @data;

my @sorted =    map  { $_->[0] }
                sort { $a->[1] cmp $b->[1] }
                map  { [ $_, (split /:/)[1] ] } @data;

print "data = \n@data\n";
print "sorted = \n@sorted\n";

__DATA__
area1:place1:name1
area1:place4:name2
area3:place3:name3
area5:place2:name2
[download]

Produces:

data =
area1:place1:name1 area1:place4:name2 area3:place3:name3 area5:place2:
+name2
sorted =
area1:place1:name1 area5:place2:name2 area3:place3:name3 area1:place4:
+name2
[download]

Update:For more information on the Schwartzian Transform, read Tom Christiansen's "Far More Than Everything You've Ever Wanted To Know About Sorting" paper.
Update 2:Changed example data to make it more obvious what was going on.