http://www.perlmonks.org?node_id=434748


in reply to Perplexed by typeglobs.

For each identifier in a package, there is a symbol table entry containing slots for each of the possible types with that identifier as its "name". E.g. if we have a variable $x, a subroutine &x, an array @x, these are all held in a typeglob *x. If one sets *y = *x, then *y contains the same slots that *x does, so, for example, $y is the same as $x. One can access slots of a typglob: for example, *x{SCALAR} is a reference to $x. Using typeglobs or references to typeglobs one can pass filehandles to a subroutine. For example,
sub blah { my $filehandle = shift; print $filehandle "Blah!\n"; } blah(*STDOUT); #these both blah(\*STDOUT); #produce Blah! (and a newline)
chas
(Updated to fix typo.)