#! perl -w
use strict;

my $fname = shift;
my $fh;
if( $fname eq '-test' ) {
    $fh = \*DATA;
}
elsif( $fname ) {
    open $fh, '<', $fname or die $!;
}
else {
   $fh = \*STDIN;
}

while( <$fh> ) {
    print;
}


__DATA__
my
test
data