<massage>
#!/usr/bin/perl -w
use strict;
my $file  = shift;                #always!
my $start = quotemeta shift;    #quote meta chars
my $end   = quotemeta shift;    #quote meta chars
my $outfile = "$file.out";
open(IN, "<$file") || die "Can't open $file!\n";
open(OUT, ">$outfile") || die "Can't open $outfile!\n";
my $file_contents = do {local $/; <IN>};     #slurp!
while ($file_contents =~ /($start.*?$end)/gs) {      
    print OUT $1, "\n";
}
</massage>

__infile__
 blah blah blah
#BG blah blah blah
 blah blah blah
#EN
 blah blah blah
 blah #BG blah #EN blah
 blah blah blah

__infile.out__
#BG blah blah blah
 blah blah blah
#EN
#BG blah #EN
[download]

--

flounder