I usually do this sort of thing in following manner:

open FH, "<fh.txt" or die "$!\n";

while (<FH>) {

   push(@y, $_), next if $flag;

   /^RE$/ and push(@y, $_), $flag++;

}

close FH;
[download]

This keeps things a bit more efficient, as it
minimalizes the amount of superflous tests --
why continue the extra overhead ( however minimal )
of checking for /^RE$/ after we already know
it's been met?