Oooh! Ohhh! I always wanted to say this ...

You shoud use strict.

Also you might not want to use the variable names $a and $b because of how sort works.
Update with Example:

Plankton@Chum_Bucket:~/perl/perlmonks> cat scritp.pl
#!/usr/local/bin/perl
use strict;
require "ex.txt";
my $bb = "blue\n";
&numbers ( $bb );
Plankton@Chum_Bucket:~/perl/perlmonks> cat ex.txt
sub numbers {
        my $v = shift;
        print "$v"
     }
 
1;
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