Looks like a wildcard mask is just the bitwise negation of a regular mask.

my $mask_wild_dotted = '0.0.0.31';
my $mask_wild_packed = pack 'C4', split /\./, $mask_wild_dotted;
my $mask_norm_packed = ~$mask_wild_packed;
my $mask_norm_dotted = join '.', unpack 'C4', $mask_norm_packed;
print("$mask_norm_dotted\n");  # 255.255.255.224
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