my $toggle = 0;   # initially false
open FH, 'file' or die "open fails: $!";
while (<FH>)
{
    $toggle = !$toggle if /USE/;
    # Not sure why you'r removing backslashes, but....
    # tr/\\//d would be faster, BTW
    s/\\//g;
    print if $toggle;
}
close FH;