nawk '
    {
	print URLdecode($0)
    }

    function URLdecode(s) {
	while(match(s,"%[0-9a-zA-Z][0-9a-zA-Z]")) {
	    code = substr(s,RSTART+1,RLENGTH-1)
	    val = 0;
	    for(i=1; i<=length(code); i++) {
	        char = toupper(substr(code,i,1))
	        val = 16*val+match("0123456789ABCDEF",char)-1
	    }
	    repl=sprintf("%c",val+0)
	    sub("%[0-9a-zA-Z][0-9a-zA-Z]",repl,s)
	}
	return(s)
    }
'