#! perl -sw
use strict;


my $term = shift;

my @section;
while( <DATA> ) {
    @section = () if /Header/;
    push @section, $_;
    if( /$term/ ) {
         print for @section;
         print while defined( $_ = <DATA> ) and not /^Header/;
         last;
    }
}

__DATA__
Header 1
just some junk
just some junk
just some junk
just some junk
just some junk
Header 2
just some junk
just some junk
just some junk
just some junk
just some junk
Header 3
just some junk
just some junk
just some junk
this is a term
just some junk
just some junk
Header 4
just some junk
just some junk
just some junk
just some junk
just some junk
Header 5
just some junk
just some junk
a different term
just some junk
just some junk
just some junk

##</code><code>##

c:\test>junk34 term
Header 3
just some junk
just some junk
just some junk
this is a term
just some junk
just some junk

c:\test>junk34 different
Header 5
just some junk
just some junk
a different term
just some junk
just some junk
just some junk