sub imgtype {
	my $file  = shift;
	my %types = (
		'BMP'	=> qr/^BM/,
		'GIF'	=> qr/^GIF8[79]a/,
		'JPEG'	=> qr/^\xFF\xD8/,
		'PNG'	=> qr/^\x89PNG\x0d\x0a\x1a\x0a/,
		'PPM'	=> qr/^P[1-6]/,
		'SVG'	=> qr/^<\?xml/,
		'TIFF'	=> qr/^MM\x00\x2a|^II\x2a\x00/,
		'XBM'	=> qr/^#define\s+/,
		'XPM'	=> qr/(^\/\* XPM \*\/)|(static\s+char\s+\*\w+\[\]\s*=\s*{\s*"\d+)/,
		);		
	if (-e $file ) {
		open(my $fh, '<', $file) or die $!;
		read($fh,my $head,11);
		close($fh);
		
		while ( my ($type,$match) = each %types ) {			
			if ( $head=~m/$match/ ) {
				return $type;				
			}
		}
		return undef;
   	}else{
   		return undef;
   	}
}


##</code><code>##

my %ALLOWED = ('GIF' => 1 ,'JPEG' => 1 );
# can be called like this 
my $Type = imgtype('some/location/image');
if ( defined $Type && $ALLOWED{$Type} ) {
   # process image
}else{
   # delete it or do whatever you want with it
}