The following works, but requires you to slurp the entire file into memory. If the file is large that might not be the best approach, I talked about a different, line-by-line approach in the recent thread about a similar topic, Multi Line Regex Matches... - basically, you'd need to keep the lines between the "start" and "end" markers in a buffer, probably an array. In regards to the following, see the documentation of the anchors ^ and $, as well as the modifiers /s, /m, and /x, in perlretut and perlre.

my $data = do { open my $fh, '<', $fn or die $!; local $/; <$fh> };
my ($test) = $data=~m{ ^\w+:\n (.+?) (?: ^\w+:$ | \z ) }msx;
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