I don't know how to exactly recreate the magic that surrounds grep, but at least it's somewhat possible by taking some magic from MeowChows treemap node :

#!/usr/bin/perl -w

use strict;

sub on {
  my($f1,$f2,$l)=@_;

  my $parmtype = ref $f1;
  print "f1: $parmtype\n";

  if ($parmtype eq 'CODE') {
    local $_=$$l;
    if (&$f1) {
      local *_=$l;
      &$f2($l);
    }
  };
}

my $foo="abba is foo";
on sub{ /foo/ }, sub { tr/ab/ba/; }, \$foo;
print "$foo\n";
on "bla", sub { tr/ab/ba/; }, \$foo;

[download]

As you see, it's still far from perfect, as you'll have to use the sub keyword for your code parameters, but at least your subroutine on can now determine through the $type parameter, whether CODE or something else was passed in.

In reply to Re: Polymorphic prototypes? (creating new syntax) by Corion
in thread Polymorphic prototypes? (creating new syntax) by kaatunut

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