i'm looking for the 3-arg equivalent to the open stmt

There isn't one. See BrowserUK's reply.

and how to use a variable for the "<<" stmt. thanks

Put a space before the <<

my $fh = \*STDOUT;
print $fh<<'EOI';    # Fails
abc
EOI
[download]

my $fh = \*STDOUT;
print $fh <<'EOI';   # Works
abc
EOI
[download]

Perl think's you're using the left shift operator with a lexical and no space.