Let me optimise your code for you:

• Firstly, you don't have to calculate $count manually. foreach does everything for you, just use $_ instead of $allcards[$count]. Or, better (see next): foreach my $card (@allcards) { ... }
• Secondly, you want to check all elements of @userinput indexed from 0 to 6. You can do it using array slice and grep:

  grep { $_ != $card } @userinput[0..6]
  [download]

  As long as grep returns arrays, you can just push it to your @resthand array.

The resulting code is:

foreach my $card (@allcards) {
 push @resthand, grep { $_ != $card } @userinput[0..6];
}
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