Michael C. Davis wrote:
> Hi, Apologies if I'm bringing up a repeated topic. I searched the
> list archive and the web and nothing specific has turned up so far.
>
> Is there a way to defer evaluation of the contents of a
> here-doc-defined value such that one can embed variables in the
> here-doc and not have them evaluated until they are used later?
> Something like this:
>
When you need to do something like that, I give them names like: <myfilename>
Then do a $header =~ s/<myfilename>/$filename/gi; at the point you want to do
the print.
Now if doing more than once, then would wnat to put into secondardy variable
to do the changes.
> code:
> -----
> use strict;
> use warnings;
>
> my $header = <<'end_of_header';
> # File: $filename
#File: <myfilename>
> end_of_header
>
> my $filename = 'xyz';
$header =~ s/<myfilename>/$filename/gi;
> print $header, "\n"; # output: want to see # File: xyz, but get #
> File: $filename
The reason you are getting $filename in this instance has to do with using
single ' vs double ". If double had been used then you would have had:
File:
Wags ;)
>
>
> I tried a few variations and nothing seems to work, as shown below.
> (This RFC http://dev.perl.org/perl6/rfc/229.html from Perl 6 implies
> that there is fact no way to do this.) Can anyone clarify. Thank
> you.
>
> code:
> -----
> use strict;
> use warnings;
>
> my $header = <<'end_of_header';
> # File: $filename
> end_of_header
>
> my $filename = "test";
>
> print $header, "\n";
> print eval { "$header" }, "\n";
> print "$header", "\n";
>
> print eval { $header }, "\n";
> print ((eval $header) ."\n");
>
> output [ .. editted for readability .. ]:
> -------
>
> # File: $filename
> # File: $filename
> # File: $filename
> # File: $filename
> Use of uninitialized value in concatenation (.) or string at
> ..\perlt\testevalsimple.pl line 15.
Any questions and/or problems, please let me know.
Thanks.
Wags ;)
Int: 9-8-002-2224
Ext: 408-323-4225x2224
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