You can also open a file handle directly against a reference to a HEREDOC as well as a scalar reference.

knoppix@Microknoppix:~$ perl -Mstrict -wE '
> open my $inFH, q{<}, \ <<EOD or die qq{open: <<HEREDOC: $!\n};
> some letters
> this line also 99 has digits
> this does not
> EOD
> 
> while ( <$inFH> )
> {
>     print if m{\d};
> }
> 
> close $inFH or die qq{close: <<HEREDOC: $!\n};'
this line also 99 has digits
knoppix@Microknoppix:~$
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I hope this is helpful.