I doo it like this:

my @shouldexist= qw(
    ismissing
    ismissing2
    isthere
    isthere2
);
my @doexist= qw(
    isthere
    isthere2
    istoomuch
    istoomuch2
);

my %missing, %toomuch;

@missing{@shouldexist}=();
# now all files that should exist have an entry

delete @missing{@doexist};
# now all that do exist don't have an entry anymore

# now the same the other way round to find superfluous files
@toomuch{@doexist}=();
delete @toomuch{@shouldexist};

print "Missing: ",join(' ',keys %missing),$/;
print "Toomuch: ",join(' ',keys %toomuch),$/;
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