You can, if you wish, open the filehandle against a reference to the HEREDOC.

$ perl -e '
-> open $fh, q{<}, \ <<EOD or die qq{open: <<HEREDOC: $!\n};
-> abc
-> def
-> EOD
-> print qq{$.: $_} while <$fh>;'
1: abc
2: def
$
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I hope this is of interest.