sub array_minus (\@\@) {
    my ( $got, $required ) = @_;
    my %required;
    @required{@required}=@required;
    delete  @required{@got};
    return values %required; 
}
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Note also that this function is not correct because the  $got $required array references passed as arguments are never used. As it stands, the code here works only because  @required @got within the function access file-scope lexicals defined earlier in the code. Also, the prototype  array_minus(\@\@) needs to be declared (or the function itself needs to be defined) before the function is invoked for prototyping to be effective.

c:\@Work\Perl\monks>perl
use strict;
use warnings;

sub array_minus (\@\@);

my @got      = qw(blue_shirt hat jacket preserver );
my @required = qw(preserver sunscreen water_bottle jacket);

# ---------- as custom function

warn "Skipper is missing: ", array_minus(@got,@required);

sub array_minus (\@\@) {
    my ( $ar_got, $ar_required ) = @_;
    my %required;
    @required{@$ar_required} = @$ar_required;
    delete  @required{@$ar_got};
    return values %required;
}

__END__
Skipper is missing: water_bottlesunscreen at - line 11.
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