[SPOILER] Perl 'Easy' Quiz of the Week #2005-1

Well, umm..this is my first post to this list, so hopefully I don't 
break anything.

My solution wasn't too fantastic, but it works. I load every prefix into 
a hash key, and the value of each key is an array of suffixes.

#!/usr/bin/perl -w

use strict;

my ($in, $out) = @ARGV;
my %prefixes;

open(IN, '<', $in) || die $!;
open(OUT, '>', $out) || die $!;

while(<IN>)
{
   chomp(my $line = $_);
   if($line =~ /^\w+\.[A-Z]$/)
   {
       my ($prefix, $suffix) = split(/\./, $line);
       $prefixes{$prefix} = () if(!$prefixes{$prefix});
       push @{$prefixes{$prefix}}, $suffix;
   }
}

for my $pref (sort keys %prefixes)
{
  
   push @{$prefixes{$pref}}, 'M' if(!search('M', @{$prefixes{$pref}}));
   print OUT map{"$pref.$_\n";}sort @{$prefixes{$pref}}
}

close(IN);
close(OUT);

sub search
{
   my ($f, @arr) = @_;
   map{return 1 if /^$f$/}@arr;
   return 0;
}