use IPC::Run 'run';
my $file = $ARGV[0] || die;
my $line;
run [ qw(ffprobe -show_streams),$file ], '&>', \$line || die "$!\n"; 

my ($width,$height);
for (split /\n/,$line) {
	$width = $1 if /width=(\d+)/;
	$height = $1 if /height=(\d+)/;
#	...
	$_ eq '[/STREAM]' && defined $width && defined $height && print "${width}x${height}\n" && last
}