[Richard Suchenwirth] 2004-05-12 - "Quoted-printable" is a way of encoding 8-bit characters by using only 7-bit ASCII characters, by replacing them with =XX, XX being two hex digits. This is used for instance in MIME mail attachments ( http://www.faqs.org/rfcs/rfc2045.html has many details). Decoding this type of data goes in a one-liner with [subst]:

 proc quoted-printable s {subst -nocom -novar [string map {=\n "" = \\u00} $s]}

The other way it seems to need explicit iteration:

 proc to-quoted-printable s {
    set res ""
    foreach char [split $s ""] {
        scan $char %c i
        if {$i>255} {error "character $i does not fit in 8 bits"}
        append res [expr {$i<128? $char: [format =%02X $i]}]
    }
    set res
 }
# Test and demo:
 % to-quoted-printable "Schöne Grüße"
 Sch=F6ne Gr=FC=DFe

Note that \u00XX was used in the decoder in place of \xXX, which is "greedy" and takes as many hex characters as it can get, working only on the last two of them.
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