Perl is always is known for their flexibility (There is more than one way to do it).
Followings are the quick way to check if a value exist in an array.
do_something if 'flour' ~~ @ingredients # ~~ operand. BEWARE: it is broken.
do_something if grep {$_ eq 'flour'} @ingredients # grep (slower than 'any')
do_something if any {$_ eq 'flour'} @ingredients # List::MoreUtils / Util::Any
do_something if any(@ingredients) eq 'flour' # use syntax 'junction';
do_something if @ingredients->contains('flour') # added with autobox
