Lady, EVOLVED 
prrgrrmmng
sed 's/`/`%60`/g;s/[\]/`%5C`/g;s/%[0-9A-F]\{2\}/`&`/g' | tr '`' '\n' | sed '/^%[0-9A-F]\{2\}$/!s/%/`%25`/' | tr '`' '\n' | awk '$0!~/%/{printf("%s",$0)}/%/{sub("%","0x");printf("\\%04o",$0)}' | xargs -0 printf '%b'
Follow
prrgrrmmng
what she had:
› awk '$0!~/%/{printf("%s",$0)}/%/{sub("%","0x");printf("\\%04o",$0)}'
the portable awk script:
› awk '$0!~/%/{printf "%s",$0}/%/{sub("%","0x");cmd="xargs printf \"%04o\"";printf "%s","\\";printf "%s",$0|cmd;close(cmd)}'
re: prrgrrmmng
for some reason gawk thinks that printf should not interpret its arguments the same as printf on the command line so instead you have to pipe to it if you need that bit