Lets get the basics that a lot of people will mention out of the way up front:

• use strict; use warnings at the top of the script.
• open ... or die "Could not open $filename, reason: $!\n";
• Three arg open, with lexical filehandles is good too:

  open my $inFH, '<', $filename or die "...";
  [download]

Perl should then tell you about how there is no function (& vs $) called "outfile", among other things

Also my $file = @files is probably not going to do what you want. Array in scalar context gives the count of items in the array.