Use Set::Scalar.

use Set::Scalar;

my $bigset   = Set::Scalar->new(@bigarray);
my $smallset = Set::Scalar->new(@smallarray);

my $difference = $bigset - $smallset;
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This assumes though that you don't care about array order, and don't care about duplicates - you're treating them as sets.

Preserving order, and assuming you're on Perl 5.10+, you can just use smart match instead...

my $smallarray_ref = \@smallarray;
my @difference = grep { !($_ ~~ $smallarray_ref) } @bigarray;
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