I'm not sure wether you mean "delete everything until the string 'RE' is encountered" or "delete everything until an RE is encountered."

For simplicity's sake I'll go with the former.

#!/usr/bin/perl -w

use strict;

my $found = 0;

while (<>) {
        if ($found or /RE(.*?)/) {
                $found = 1;
                print;
        }
}
[download]

I love unix:

[ar0n@zendo perl]$ perl re.pl < INPUT > OUTPUT
[download]

[ar0n]