# Fetch all .zip files in the incoming directory 
my @zipfiles = glob "$srcDir/*.zip";

# Scan through the files to find out which XXX bits may exist
my %XXXlist;
for my $file (@zipfiles) {
   if ($file =~ /(alphat|numerict|updatet).(.*).zip/) {
      # OK one of our desired prefixes match, second capture group is a valid XXX value
      $XXXlist{$2}++;
   }
}

# Now we can go on and see what we can process
for my $XXX (keys %XXXlist) {
   if (-E "$srcDir/alphat.$XXX.zip" 
           and -E "$srcDir/numerict.$XXX.zip" 
           and -E "$srcDir/updatet.$XXX.zip") {
      # all files are found, so go do some work
   }
   else {
      # Not all files are present yet.
   }
}