how can I join a range of lines in sed?

[Tom Christiansen]

>From the keyboard of psrc at mtunq.att.com (Paul S. R. Chisholm):
:I have a file with sections inside BEGIN/END pairs.  (In 99% of the
:interesting cases, there are only either one or two lines between the
:two dot lines, if that makes any difference.)  I want to "join" (in the
:sense of the ed/ex/vi command) the lines together, and delete the
:sentinel lines.  I could do this easily enough in awk, but the rest of
:the job is done in a sed script, and I'd like to keep all the work
:together if I can.

I find it more difficult than it should be in sed to do relatively 
simple things.  Awk's more traditional control structures seems
to be easier on my brain.  

:Somehow, I need to use the sed N command to "append the next line of
:input to the pattern space with an embedded newline."  Without the N,
:the pattern space consists of only one line at a time.  I've tried
:substitutions and the t command (yuchh, I haven't used an if/goto
:statement in over a decade!), but it never quite worked; e.g, this:

You might consider running your whole script through s2p, the sed-to-perl
translator.  This would yield you the more traditional control structures
instead of sed's gotos and other oddities.  For the part that you posted,
this works:

    #!/usr/bin/perl -n
    if (/^BEGIN/ .. /^END/)  {
	if (/^BEGIN/) {
	    $hold = '';
	} elsif (/^END/) {
	    $hold =~ s/\n/ /g;
	    $hold =~ s/ $//;
	    print ".FOO \"$hold\"\n";
	} else {
	    $hold .= $_;
	}
    } else {
	print;
    } 

I just find this kind of thing easier to read than cryptic sed scripts.

--tom