There's no problem with your for loop, since you are not removing elements from the list over which the for loop iterates. There are two things you could do to achieve the same result in a more perl-ish way. Use a hash to know if an element exists in the @find list, and use grep to turn your input list into another one:

my @in = (1, 2, 3, 4, 3, 5, 3);
my %find = map { $_ => 1 } (3,4);
my @out = grep { !exists $find{$_} } @in;
# or: @out = grep !$find{$_}, @in;
say for @out;
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Edit: I meant "two things", not "two thinks", obviously.
Also added the short version of the grep.