Similar to talexb's idea, no where near as cool as merlyn's code, here is another way to do it: 
use strict;

while(<DATA>) {
    my ($preserve) = $_ =~ /STARTPRESERVE(.*?)STOPPRESERVE/;
    s/$preserve// if $preserve;
    s/\s+/ /og;
    s/STARTPRESERVESTOPPRESERVE/$preserve/ if $preserve;
    print;
}

__DATA__
A Bridge Too Far     Hosted by Rod Stuart     Friendly Skys
42        STARTPRESERVE Life, the universe...    and      Everything  
+   STOPPRESERVE   X-Files
HotWheels are cool     More movies on Fox           File server

[download]
UPDATE: you are one sick twisted puppy I0! ;)

UPDATE UPDATE: that's it - i'm outta here ...

jeffa travels to the highest mountain to meditate more perlre

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

In reply to (jeffa) Re: RegEx to filter \s not between labels by jeffa
in thread RegEx to filter \s not between labels by gryphon

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