Indented HEREDOC?

[Withigo]

Dear Monks,
Several times I've found myself wishing I could indent the string that terminates a HEREDOC in order to align the entire HEREDOC with its containing sub/block(and also for nefarious-but-inspiring obfuscation & japh purposes).

i.e.,

if ($foo) {
  print <<STRING;
  foo is $foo.
  STRING
}

Is this trivial enough to be capable of being added to perl5? Hopefully it'll be an option in Perl 6. But in the mean time, does anyone know if there's a source filter that accomplishes this?
Thanks!

[lidden]

It will be added to Perl 6, I think it will be the default.

[kudra]

I think Filter::Indent::HereDoc does this. I haven't used it, however.

[Ovid]

I posted a snippet which will handle this at Unindent HERE docs. Also, if you want to indent the closing token, put the leading token in quotes.

print <<'    END';
    This is text.
    END

[reasonablekeith]

sorry for the nit-pick, but given the OP's example showed a variable, the example really should have been.

if ($foo) {
  print <<"  STRING";
  foo is $foo.
  STRING
}

With the difference being that I've used double quotes and not single quotes. I mention it becuase I missed this the first time I saw heredocs, and didn't realise it caused the entire contents of the heredoc to be either interpolated or not, dependant on whether you used double or single quotes, respectively.

The output of the above would obviously be


foo is whatever_is_in_foo

as opposed to single quotes, which would give


foo is $foo

[Ovid]

No need to apologize for the nitpick. It's a point well-taken.

[mantadin]

One workaround maybe:

    ($v = <<"    END") =~ s/^\s+//gm;
    foo bar
    and so on
    END

[vek]

Take a peek at Filter::Indent::HereDoc, it does exactly what you need.

[YuckFoo]

Withigo

I use the quote operators in place of heredocs whenever possible (perlop), because it looks better. This adds a leading newline and trailing whitespace to the string, but when that's not important, I like it.

QqFoo

if ($foo) {
  print qq {
    foo is $foo.
  };
}

[LanX]

Since this thread was my top-hit in google (YMMV):

Intended Here Documents were introduced with 5.26.

Indented Here-documents

This adds a new modifier "~" to here-docs that tells the parser that it should look for /^\s*$DELIM\n/ as the closing delimiter.

These syntaxes are all supported:

<<~EOF;
<<~\EOF;
<<~'EOF';
<<~"EOF";
<<~`EOF`;
<<~ 'EOF';
<<~ "EOF";
<<~ `EOF`;

The "~" modifier will strip, from each line in the here-doc, the same whitespace that appears before the delimiter.

Newlines will be copied as-is, and lines that don't include the proper beginning whitespace will cause perl to croak.

For example:

if (1) {
  print <<~EOF;
    Hello there
    EOF
}

prints "Hello there\n" with no leading whitespace.

Probably my favourite improvement since // defined-or.