c:\@Work\Perl\monks>perl -wMstrict -le
"my $string = qq{test\nI\nwant length of this line\n test};
 my $position = 12;
 ;;
 my $length_of_line;
 if ( $string =~ /\n.*(?=\n)/ && $-[ 0 ] < $position && $+[ 0 ] > $position ) {
   $length_of_line = $+[ 0 ] - $-[ 0 ];
   }
 print $length_of_line;
"
Use of uninitialized value in print at -e line 1.