prototype
Returns the prototype string of a subroutine, or undef if none.
Accepts a code reference, a reference to a CV, or a string naming
the subroutine. For CORE:: builtins, returns the well-known
prototype from a built-in table (e.g. \@@ for push, ;$ for
defined). For user-defined subs, looks up the CV in the stash
and returns its prototype. Unqualified names are resolved in the
current package. Returns undef when the subroutine has no
prototype or cannot be found.
Synopsis
my $proto = prototype(\&mysub); # "$$"
my $proto = prototype('CORE::push'); # "\@@"
my $proto = prototype('main::func'); # look up by name