...
my ($record, $date, $outfile, %stations, $sstation, $linecnt, $pcntg, @values);

...
$date = $ARGV[1];
%stations = map{ $_ => 1 } @ARGV[ 2 .. $#ARGV];
... 
if( $values[0] eq $date && exists $stations{ $sstation } ) {

##</code><code>##

perl midasproc2.pl midas_wxhrly_199901-199912.txt "1999-12-15 11:00" 19260 19261 19262 [...]