Yeah, I commented above that I had forgotten strict and mistakenly thought Inf was parsed as a number.

But, this is my point - right now the character is illegal in a perl script, and there's no reason (that I can guess, having not looked at perl's internals yet) that the language parser couldn't use that as a permitted character for numeric literals. It would be a little different from 'inf' in that it would be parsed as the constant rather than a lexical function that returns a constant, so like "-∞" would immediately become an NV, where "-inf" is a negation of a function call that hopefully gets resolved to an NV during compiler optimizations.

Edit

I mean exactly this :-)

$ git diff --cached
diff --git a/toke.c b/toke.c
index e6ff0c4f74..4590774e44 100644
--- a/toke.c
+++ b/toke.c
@@ -9174,6 +9174,13 @@ yyl_try(pTHX_ char *s)
                 return tok;
             goto retry_bufptr;
         }
+       if (UTF && s + 2 < PL_bufend && *s == '\xE2' && s[1] == '\x88'
+ && s[2] == '\x9E') {
+           pl_yylval.opval = newSVOP(OP_CONST, 0, newSVnv(NV_INF));
+           s += 3;
+           if (PL_expect == XOPERATOR)
+               no_op("Number",s);
+           TERM(THING);
+       }
         yyl_croak_unrecognised(aTHX_ s);
 
     case 4:
[download]

$ PERLLIB=lib ./perl -E 'use utf8; say∞;'
Inf
$ PERLLIB=lib ./perl -E 'use utf8; say -∞;'
-Inf