Enhance support for floating point numbers

Floating points numbers (eg. `2.34`, `.54`) were not being matched
correctly. This patch splits the number class regex in different variants to
make things clearer and also adds variants to better match floating points,
including the `_` character, and also the special case of version numbers
(eg. v5.38). Markup test for the new number class was also added.

src/languages/perl.js

@@ -271,6 +271,22 @@ export default function(hljs) {
       relevance: 0
     }
   ] };
+  const NUMBER = {
+    className: 'number',
+    variants: [
+      // in Perl numbers can have '_' in the middle, but not at the end,
+      // so we lookbehind the '\b' for a non-trailing '_'.
+      // decimal numbers
+      { match: /0?\.[0-9][0-9_]+(?<!_)\b/ },
+      // include the special versioned number (eg. v5.38)
+      { match: /\bv?(0|[1-9][0-9_]*(\.[0-9_]+)?|[1-9][0-9_]*)(?<!_)\b/ },
+      // non-decimal numbers
+      { match: /\b0[0-7][0-7_]*(?<!_)\b/ },
+      { match: /\b0x[0-9a-fA-F][0-9a-fA-F_]*(?<!_)\b/ },
+      { match: /\b0b[0-1][0-1_]*(?<!_)\b/ },
+    ],
+    relevance: 0
+  }
   const STRING_CONTAINS = [
     hljs.BACKSLASH_ESCAPE,
     SUBST,
@@ -385,11 +401,7 @@ export default function(hljs) {
         }
       ]
     },
-    {
-      className: 'number',
-      begin: '(\\b0[0-7_]+)|(\\b0x[0-9a-fA-F_]+)|(\\b[1-9][0-9_]*(\\.[0-9_]+)?)|[0_]\\b',
-      relevance: 0
-    },
+    NUMBER,
     { // regexp container
       begin: '(\\/\\/|' + hljs.RE_STARTERS_RE + '|\\b(split|return|print|reverse|grep)\\b)\\s*',
       keywords: 'split return print reverse grep',

test/markup/perl/number.expect.txt

@@ -0,0 +1,26 @@
+<span class="hljs-keyword">use</span> <span class="hljs-number">v5.38</span>;
+<span class="hljs-keyword">use</span> <span class="hljs-number">5.0020</span>;
+
+<span class="hljs-keyword">my</span> $number = <span class="hljs-number">9</span>;
+$number = <span class="hljs-number">0</span>;
+$number = 0_;
+$number = <span class="hljs-number">0.99</span>;
+$number = <span class="hljs-number">99</span>;
+$number = <span class="hljs-number">00</span>;
+$number = 99__;
+$number = <span class="hljs-number">99.9</span>;
+$number = <span class="hljs-number">99.99</span>;
+$number = .99_;
+$number = ._99;
+$number = <span class="hljs-number">0x99FF</span>;
+$number = <span class="hljs-number">0x99_EE_FF</span>;
+$number = 0x99_EE_FF_;
+$number = 0x_99_FF;
+$number = <span class="hljs-number">0b00101011</span>;
+$number = 0b00101011_;
+$number = <span class="hljs-number">0b0010_1011</span>;
+$number = 0b_0010_1011;
+$number = <span class="hljs-number">0777</span>;
+$number = <span class="hljs-number">07_7_7</span>;
+$number = 0_777;
+$number = 07_7_7_;

test/markup/perl/number.txt

@@ -0,0 +1,26 @@
+use v5.38;
+use 5.0020;
+
+my $number = 9;
+$number = 0;
+$number = 0_;
+$number = 0.99;
+$number = 99;
+$number = 00;
+$number = 99__;
+$number = 99.9;
+$number = 99.99;
+$number = .99_;
+$number = ._99;
+$number = 0x99FF;
+$number = 0x99_EE_FF;
+$number = 0x99_EE_FF_;
+$number = 0x_99_FF;
+$number = 0b00101011;
+$number = 0b00101011_;
+$number = 0b0010_1011;
+$number = 0b_0010_1011;
+$number = 0777;
+$number = 07_7_7;
+$number = 0_777;
+$number = 07_7_7_;