#! perl -slw
use strict;

my( $a, $b ) = ( 'mya', 'myb' );

{
    my( $a, $b ) = ( 'oura', 'ourb' );
    my @sorted = sort { $a <=> $b } map{ rand 100 } 0 .. 99;
    print "$a : $b";
}
print "$a : $b";
__END__
C:\S\pl>perl sortab.pl
Can't use "my $a" in sort comparison at sortab.pl line 10.