utility: fix quote_sheetname() edge cases

Closes #308

Author: jmcnamara

lib/Excel/Writer/XLSX/Utility.pm

@@ -243,8 +243,9 @@ sub quote_sheetname {
             $needs_quoting = 1;
         }
 
-        # Rule 3. Sheet names must not be a valid A1 style cell reference.
-        # Valid means that the row and column values are within Excel limits.
+        # Rule 3. Sheet names must not be a valid A1 style cell reference. Valid
+        # means that the row and column range values must also be within Excel
+        # row and column limits.
         elsif ( $uc_sheetname =~ /^([A-Z]{1,3}\d+)$/ ) {
             my ( $row, $col ) = xl_cell_to_rowcol( $1 );
 
@@ -255,60 +256,50 @@ sub quote_sheetname {
         }
 
         # Rule 4. Sheet names must not *start* with a valid RC style cell
-        # reference. Valid means that the row and column values are within
-        # Excel limits.
-
-        # Rule 4a. Check for some single R/C references.
-        elsif ($uc_sheetname eq "R"
-            || $uc_sheetname eq "C"
-            || $uc_sheetname eq "RC" )
-        {
-            $needs_quoting = 1;
-
+        # reference. Other characters after the valid RC reference are ignored
+        # by Excel. Valid means that the row and column range values must also
+        # be within Excel row and column limits.
+        #
+        # Note: references without trailing characters like R12345 or C12345 are
+        # caught by Rule 3. Negative references like R-12345 are caught by Rule
+        # 1 due to the dash.
+
+        # Rule 4a. Check for sheet names that start with R1 style references.
+        elsif ( $uc_sheetname =~ /^R(\d+)/ ) {
+            my $row = $1;
+            if ( $row > 0 && $row <= $row_max ) {
+                $needs_quoting = 1;
+            }
         }
 
-        # Rule 4b. Check for C1 or RC1 style references. References without
-        # trailing characters (like C12345) are caught by Rule 3.
+        # Rule 4b. Check for sheet names that start with C1 or RC1 style
         elsif ( $uc_sheetname =~ /^R?C(\d+)/ ) {
             my $col = $1;
             if ( $col > 0 && $col <= $col_max ) {
                 $needs_quoting = 1;
             }
         }
 
-        # Rule 4c. Check for R1C1 style references where both the number
-        # ranges are optional. Note that only 1 of the number ranges is
-        # required to be valid.
-        elsif ( $uc_sheetname =~ /^R(\d+)?C(\d+)?/ ) {
-            if ( defined $1 ) {
-                my $row = $1;
-                if ( $row > 0 && $row <= $row_max ) {
-                    $needs_quoting = 1;
-                }
-            }
-
-            if ( defined $2 ) {
-                my $col = $1;
-                if ( $col > 0 && $col <= $col_max ) {
-                    $needs_quoting = 1;
-                }
-            }
+        # Rule 4c. Check for some single R/C references.
+        elsif ($uc_sheetname eq "R"
+            || $uc_sheetname eq "C"
+            || $uc_sheetname eq "RC" )
+        {
+            $needs_quoting = 1;
         }
     }
 
-
     if ( $needs_quoting ) {
+
         # Double quote any single quotes.
         $sheetname =~ s/'/''/g;
         $sheetname = q(') . $sheetname . q(');
     }
 
-
     return $sheetname;
 }
 
 
-
 ###############################################################################
 #
 # xl_inc_row($string)