my %apps = qw(
  gcc-3.3 1
  gcc-3.3.1 1
  gcc-3.3.2 1
  gzip-1.2.4a 1
  make-3.79.1 1
);

my %latest = ();

for(keys %apps) {
  my($program, $version) = split /-/, $_, 2;
  $latest{$program} = $version if
      not exists $latest{$program} or
      ($latest{$program} cmp $version) < 0;
}

print "make: $latest{make}\n";
print "gcc: $latest{gcc}\n";
[download]

my $package = "gcc";
my $latest_vers = (sort grep /^\Q$package\E-/, keys %apps)[-1];
[download]

And is 1.10a an alpha release of version 1.10, or patch level a of version 1.10?

Abigail

%apps = (
  gcc-3.3 => 3,
  gcc-3.3.1 => 2,
  gcc-3.3.2 => 1,
  gzip-1.2.4a => 1,
  make-3.79.1 => 1,
);
[download]

my %rpms;
my %files;

foreach my $file (<*.rpm>) {
  # RPM-SPECIFIC STUFF:
  my @result = `rpm -qp --queryformat "%{NAME}/%{ARCH}/%{VERSION}.%{RE
+LEASE}\n" $file`;
  my ($name, $arch, $version) = split /\//, $result[0];
  # END RPM-SPECIFIC STUFF
  $name .= ":" . $arch;

  if ( exists $rpms{$name} ) {
    #decide which one we like better:
    my @a = split /\./, $version;
    my @b = split /\./, $rpms{$name};
    my $i=0;
    my $max = $#a > $#b ? $#a : $#b;
    while ($i <= $max) {
      if ( $a[$i] eq $b[$i] ) {
    $i++;
    next;
      }
      if ( $a[$i] lt $b[$i] ) {
    print "rm -f $file\n";
    last;
      } else {
    my $rm = "rm -f $files{$name}";
    print "$rm\n";
    `$rm` if lc($ARGV[0]) eq 'rm';
        # or whatever else you want to do with old files.
    last;
      }
      $i++;
    }
  } else {
    $rpms{$name} = $version;
    $files{$name} = $file;
  }
}
[download]

http://search.cpan.org/~edavis/Sort-Versions-1.5/Versions.pm would seem to be the thing.

You'd just use its versioncmp() function in the sorting.

I'm not sure what its answer is to Abigail's question "is version 4.2 older or newer than version 4.10?" because I'm not in a position to test right now.

Update: Not an answer to the actual question, I now realise, but to the "I'm going to have to get creative later" part.

Thank you everyone for your responses. Since it turns out I don't greatly care about the non-latest package versions, I'll be weeding these out as I build the hash, resulting in a scan through the full data just one time, rather than for each lookup. I'll be using the application name as the key, and the latest version as the value, so I end up with with this:

%apps = (
  gcc => '3.3.1',
  gzip => '1.2.4a',
  make => '3.79.1',
);
[download]

Then I can check defined($apps{gcc}) to see if gcc is installed, and $apps{gcc} to get the latest version. Thanks saintmike for guiding me down that path.

As for determining which version is the latest in any given case, in the 150 applications in my full list, cmp works in almost every case. I handle the remaining 5 or 6 packages by exception, but I'll be looking into the Versions module that Cody Pendant suggested to try to reduce the number of exceptions. Thanks again!