c:\@Work\Perl\monks\polmed>perl test.pl
doesn't work:
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
Use of uninitialized value in numeric comparison (<=>) at personel.pm line 7.
[["amy", 35], ["bill", 55], ["george", 28], ["jason", 71]]

does work:
[["jason", 71], ["bill", 55], ["amy", 35], ["george", 28]]

also works:
[["jason", 71], ["bill", 55], ["amy", 35], ["george", 28]]

also works (somewhat slower):
[["jason", 71], ["bill", 55], ["amy", 35], ["george", 28]]

original array (should be unchanged):
[["amy", 35], ["bill", 55], ["george", 28], ["jason", 71]]