Well, I encourage you to use modules, but you can use this functions below for JPG and GIF! I put for SWF too! :-P

To use just point the file path to the right function, like in the example. For SWF the function is good to get the Flash version!

  
  my ($w , $h , $type , $version) = IMG_jpg_size('/tmp/splash.jpg') ;
  
  print ">> $w , $h , $type , $version\n" ;

#################
# IMG_OPEN_FILE #
#################

sub IMG_open_file {
  my ( $img_fl ) = @_ ;
  open(IMGSTRM, $img_fl) ; binmode( IMGSTRM );
  return( \*IMGSTRM );
}


###############
# IMG_READBUF #
###############

sub IMG_readbuf {
  my $buf ;
  read(@_[0], $buf, @_[1]) ;
  return( $buf ) ;
}

#######
# JPG #
#######

sub IMG_jpg_size {
  my($JPEG) = IMG_open_file(@_) ;
  my($done)=0;
  my($c1,$c2,$ch,$s,$length, $dummy)=(0,0,0,0,0,0);
  my($a,$b,$c,$d);
  
  if (
      defined($JPEG)
      && ($c1 = &IMG_readbuf($JPEG,1))
      && ($c2 = &IMG_readbuf($JPEG,1))
      && ord($c1) == 0xFF
      && ord($c2) == 0xD8 ) {     

    while (ord($ch) != 0xDA && !$done) {

      while (ord($ch) != 0xFF) { return('error') unless ($ch = &IMG_re
+adbuf($JPEG,1)) ;}
      while (ord($ch) == 0xFF) { return('error') unless ($ch = &IMG_re
+adbuf($JPEG,1)) ;}

      if ((ord($ch) >= 0xC0) && (ord($ch) <= 0xC3)) {
        return('error') unless ($dummy = &IMG_readbuf($JPEG,3)) ; 
        return('error') unless ($s = &IMG_readbuf($JPEG,4)) ;
        ($a,$b,$c,$d)=unpack("C"x4,$s);
        return ($c<<8|$d, $a<<8|$b , 'jpg');
      }
      else {
        return('error') unless ($s = &IMG_readbuf($JPEG,2)) ;
        ($c1, $c2) = unpack("C"x2,$s);
        $length = $c1<<8|$c2;
        last if (!defined($length) || $length < 2);
        $dummy = &IMG_readbuf($JPEG,$length-2);
      }
    }
  }

  return ('error');
}

#######
# GIF #
#######

sub IMG_gif_size {
  my($GIF) = IMG_open_file(@_) ;
  my($a,$b,$c,$d)=(0,0,0,0,0);
  
  my $type = &IMG_readbuf($GIF,6) ;
  my $s = &IMG_readbuf($GIF,4) ;
  
  if(defined( $GIF )
     && $type =~ /GIF8[7,9]a/
     && length($s) == 4 ) {
    ($a,$b,$c,$d)=unpack("C"x4,$s);
    return ($b<<8|$a,$d<<8|$c,'gif', "\L$type\E");
  }
  return ('error');
}

#######
# SWF #
#######

sub IMG_swf_size {
    my($SWF) = IMG_open_file(@_) ;
    my $header = &IMG_readbuf($SWF,33) ;
    
    if (defined( $SWF ) && substr($header , 0 , 3) =~ /FWS/) {
    sub IMG_swf_bin2int { unpack("N", pack("B32", substr("0" x 32 . sh
+ift, -32))); }

    my $ver = IMG_swf_bin2int(unpack 'B8', substr($header, 3, 1));
    my $bs = unpack 'B133', substr($header, 8, 17);
    my $bits = IMG_swf_bin2int(substr($bs, 0, 5));
    my $x = int(IMG_swf_bin2int(substr($bs, 5+$bits, $bits))/20);
    my $y = int(IMG_swf_bin2int(substr($bs, 5+$bits*3, $bits))/20);
    return ($x, $y , 'swf' , $ver);
    }
    
    return ('error');
}

#######
# END #
#######

1;
[download]

Graciliano M. P.
"The creativity is the expression of the liberty".