# make the @$all array the union of everything in
# either @$all or @$accounts, excluding the acc 44443 record
# (if it exists at all) and exclude any possible duplicates
# This "zaps" the duplicate 54321 record.

# This literally says, "transfer the input to the output if
# the input record isn't about account 44443 and we haven't
# already transferred that record to the output before.  
# This assumes that records are uniquely id'ed by the acc
# number. That might or might not be true in the actual
# application.

my %seen;
@$all = grep{ $_->{acc} ne '44443' and !$seen{$_->{acc}}++ } @$all,@$accounts;