Replacing sed for zsh portability

[DervishD <zsh@dervishd.net>]

    Hi all :)

    I'm going to release some scripts, and they have the
documentation within the own script. In my system I extract it using
GNU sed, but now I cannot do it since I'm using a GNU extension. In
order to avoid the non-portable '\|' sed regex operator, I must do
the following:

    sed -ne '/<=$/,/=>$/p' < $0 | while read line
    do
        print -- ${${line#\#}#(<=|=>| )}
    done

    The documentation is enclosed between "<=" and "=>" delimiters,
something like this:

#<=
# This is an example of documentation
# Here are more lines
#
# Yet even more lines here
...
#=>

    Since I cannot use sed for the entire work unless I complicate
the script (doing multiple substitutions and the like), I want to get
rid of the current script and doing all the job in ZSH. It doesn't
matter if it is very slow, speed here is not an issue.

    Can this be done in zsh easily or the only way is to use a while
loop to ignore lines before the delimiter and another to process the
documentation itself? Otherwise I'll try to write a portable sed
script, although I would prefer to remove any dependency except for
zsh itself of course.

    Another question, related to this. It seems that the X|Y glob
operator doesn't work left-to-right, but shortest-first. If I do
this:

    print ${line#\#(<=|=>| |)}

    then the 'nothing' at the end is used as the match, and the
delimiters are not matched. Is doing two substitutions the only way
(as I'm doing currently)?

    Thanks a lot in advance :)

    Raúl Núñez de Arenas Coronado

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