use strict;
use File::Find;

die "usage $0 <dir>" unless (@ARGV == 1 && -d $ARGV[0]);
find (
    sub {
        return unless -f $_;
        open (FILE, "< $_") or warn "cannot read $_\n" and return;
        my @lines = grep {!(/inserted banner/i .. /end of inserted banner/i)} <FILE>;
        close (FILE);
        open (FILE, "> $_") or warn "cannot write $_\n" and return;
        print FILE @lines;
        close (FILE);        
   },
   $ARGV[0]
);