Take a reference or let Prototypes do it for you

#!/usr/bin/perl --
use strict;
use warnings;
sub istg(*) { warn shift }
sub istgg { my $f = shift; my $ff=\$f; warn "$f $ff" }
istg(1);
istgg(1);
istg(*ARGV);
istgg(*ARGV);
__END__
1 at - line 4.
1 SCALAR(0x99ba0c) at - line 5.
GLOB(0x99b5bc) at - line 4.
*main::ARGV GLOB(0x99ba0c) at - line 5.
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