If I'm understanding you correctly (not entirely sure), you could use pack/unpack to convert your hex string "0xffff...fffe" into an ASCII "bit"-string, i.e. where each byte of the string is either the character "1" or "0". You would then simply use substr to test whether the char at a specific index is "1", which would mean the VLAN with that number/index is allowed.  Something like this (simplified):

my $h = "ff00f0fe";  # just 32 bits here, but any other length possibl
+e

my $b = unpack("B*", pack("H*", $h));

print "$b\n";        # 11111111000000001111000011111110

my $idx = 5;
my $allowed = substr($b, $idx-1, 1) eq "1";
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Note that you need to remove the leading "0x" from the string.