my %REGEX = (
    header    = [qr/^(?!START:|END:)([^*: ][^:]+):(.+)\n/, \&header],
    starttime = [qr/^START:\s*(.+)\n/, \&etc],
    endtime   = [qr/^END:\s*(.+)\n/, \&etc],
    lineitem  = [qr/^(?:\* |  )([^:]+):(\d+):(.+)\n/, \&etc]
);
#...
#You could even use constants here to make things easier.
# 0 = RE; 1 = FUNCTION; or something.
for my $rex_table (keys %REGEX) {
  if (my @m = $line =~ $rex_table->[0]) {
    $rex_table->[1]->($r,@m);
    next LINE;
  }
}