I tried all of your snippets, and none seemed to work. For instance:

perl -le 'print join " ", map {ord pack "H2", $_} shift =~ /../g' 396
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I'd expect to get: 0011 1001 0110, but instead I get 57, which isn't very binary at all :)

Similarly with decode:

perl -le 'print unpack "H*", pack "C*", @ARGV' 0011 1001 0110
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Results in 0be96e (hex!) instead of 396.

These should work:

# encode
perl -e 'print sprintf("%04b ",$_) for shift =~ /\d/g' decimal

#decode
perl -e '$p=1; map{$l+=oct("0b$_")*$p;$p*=10} reverse @ARGV; print $l'
+ bcddigit1 bcddigit2 etc
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Update: Updated decoder to use 5.6.1's oct("0b") feature instead of the old perlfaq way to convery binary to decimal.