It depends. Do you enter the whole contents of the file at once or line/record by line/record?

sub check_and_insert_into_database {
  my $filename = shift;
  open my $handle,"<",$filename or die "Can't open $filename: $!";
  local $/; # read whole file instead of line-by-line
  my $contents = <$handle>;
  return if ($contents =~ /CLEAR/);
  # insert $contents into database
}
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update: see also perlretut and perlre, perlvar (for the $/ variable) and perlfaq7 and perlsub (for info on local() )