syntax: perl: avoid recognizing embedded hash signs as a comment starter

Require that a comment starts at the start of a line or is preceded by
whitespace.  This prevents most hash signs used for other purposes (and
what follows them) getting colored as comments.

syntax/perl.nanorc

@@ -11,5 +11,8 @@ icolor cyan start="[$@%]" end="( |[^0-9A-Z_]|-)"
 color yellow "".*"|qq\|.*\|"
 color white "[sm]/.*/"
 color white start="(^use| = new)" end=";"
-color green "#.*"
+
+# Comments.
+color green "(^|[[:space:]])#.*"
+
 color yellow start="<< 'STOP'" end="STOP"