print "${hello}goodbye";
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Update: I find it somewhat amusing that no one (as of this posting) pointed fx's obvious solution. So I can't help but wonder, are there inherent problems with his solution, or does one person suggesting a solution lead the PerlSheep (that would include me) down a narrow path?

In this situation: print $hello, "goodbye\n"; would also work I believe, and clearly separates the variable from the string. == fx, Infinity is Colourless

Note that this code fails:

my $R = 'Twenty';
print "$R_Something_[1]";
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Russ
Brainbench 'Most Valuable Professional' for Perl

I read your example, and wondered how this would interpolate:

my $R="foo";
print "${R}[0]\n";
[download]

I thought it would either interpolate $R and print foo[0], or interpolate as $R[0], and print an empty string. Instead, I got an unexpected result:

[0]
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Anyone know why? I have a feeling I might be missing something in the meaning of ${R}[0].

These act in the expected way:

my $R = "foo";
my $R[0] = "bar";
print "${R}\[0]\n";
print "${R[0]}\n";
[download]

Any enlightenment?

Alan

Update: Ah, that makes sense, a bit too subtle for me to get without some help. Thanks!

Okay, you made $R lexical with my. ${R} is a symbolic reference to the scalar variable named 'R'. Just left alone, Perl will figure out you want the lexical variable and not a variable in the symbol table.

Looking for ${R}[0], however, perl -w says this:
Name "main::R" used only once: possible typo at - line 2.

So, when you add characters that look like a variable specification Perl is only looking in the symbol table.

If you don't make $R lexical, it will work like you originally expected:

$R="foo";
print "${R}[0]\n";
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prints "foo[0]"

To get perl to keep interpolating, just keep adding {}'s:

use vars qw/$R @foo/;
$R="foo";
@foo = (42);
print "${${R}}[0]\n";
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prints 42

:-)

BTW, I seem remember some code posted some time ago which did this kind of "multiple interpolation." I can't find it. Anyone know what node that is (or am I just hallucinating again?
("Too much LDS" -- Kirk about Spock in ST:IV))

Update: Here it is: Double Interpolation of a String

Russ
Brainbench 'Most Valuable Professional' for Perl

print "Name is $obj->name";
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...right then and there?

/jeorgen

Here you go:

sub yahoo()
{
    return "Easy";
}

print "${\yahoo()} does it!\n";
[download]

Never mind the odd sub naming convention, it is the result of too little sleep. :)
Cheers!

Oh, you asked for it!

Mark-Jason Dominus presented this at the Perl Conference. It's a generic way to evaluate a Perl expression inside a double-quoted string:

package Eval;

sub import
{
    my ($package, $name) = @_;
    $name = 'Eval' unless defined $name;
    my %magical_hash;
    tie %magical_hash =>Eval;
    my $caller = caller;
    
    *{caller . '::' . $name} = \%magical_hash;
}

sub TIEHASH
{
    my $self = \'fake';
    bless $self => Eval;
}

sub FETCH 
{
    my ($self, $value) = @_;
    $value;
}
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Looks pretty freaky, eh? Okay, now try this:

use Eval => ':';

$salary = 43_000;
print "After your raise, you will make $:{$salary*1.06}.\n";
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Yeek. Have fun!

Thanks for the example, CMonster, but I don't get it to work on my machine (ActiveState 5.005_03).

I get:

Warning: Use of "caller" without parens is ambiguous at C:\... line 11. syntax error at C:\... line 29, near "use Eval =>"

So I change from:

use Eval => :;

to:

use Eval ( ':');

at line 29.

Then I get:

Modification of a read-only value attempted at Eval.pm line 17

and that one I just don't know what to do about. I tried to change

my $self = \'fake'

to:

my $self = {}

at line 16, but that didn't help.

/jeorgen