$text =~ s/#([^#]+)#/$hash{$1}/g
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$text =~ s/\#(\w+)\#/$hash{$1}/g;
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-----------------------------------------------------
Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important

--
notsoevil
--
Jeremiah 49:32 - And their camels shall be a booty. . .

When doing substitutions like this, /e is your friend.   $text =~ s/\#\w+\#/$hash{$1}/eg; /e forces the right-hand side of the s/// to be evaluated as a Perl expression, and the result substituted for whatever the left-hand side matched. The boundary between interpolation and substitution can seem pretty hazy, but it makes a bit more sense if you imagine that the regexp is "compiled" immediately before it is executed. At that point, $1 either doesn't have a value, or holds a value from a prior regexp. Neither is what you want.

Consult perlre for full details.

Perhaps it shouldn't work without /e, but it does, at least with activestate perl 5.6.1. (obviously, you should use strict and warnings...)

#!perl
$_="this is a #fish#\n";
$a{"fish"}="test";
print;
s/#(\w+)#/$a{$1}/;
print;

this is a #fish#
this is a test

C:\perl -v

This is perl, v5.6.1 built for MSWin32-x86-multi-thread
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2001, Larry Wall

Binary build 626 provided by ActiveState Tool Corp. http://www.ActiveS
+tate.com
Built 01:31:15 May  2 2001
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Have you read what the /e switch does? I sugguest you do.

Your argument basically boils down to s/#(\w+)#/$variable/; in which $variable gets expanded, as it will no matter what (if /e is there or not).

Compare this to:

#!perl -w
use strict;
my %hashola = (fish => "test" );

sub f($){ return $hashola{shift @_};  }

my $rock = "this is a #fish#\n";
my $block = $rock;

print $rock;

$block =~ s/#(\w+)#/&f($1);/; # expands $1, doesn't call &f

print $block;

$block = $rock; # restoree

$block =~ s/#(\w+)#/$hashola{$1}/; # expands the variable

print $block;

$block = $rock; # restoree

$block =~ s/#(\w+)#/&f($1)/e; # calls the function

print $block;

$block = $rock; # restoree

$block =~ s/#(\w+)#/$hashola{$1}/e;

print $block;

$block = $rock; # restoree

__END__
F:\dev>perl f
this is a #fish#
this is a &f(fish);
this is a test
this is a test
this is a test

F:\dev>
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Ok ok, from perlop (since s is an operator), I quote:

e Evaluate the right side as an expression.

Unless you escape $hashname{$1} like \$hashmane{$1}, the actual variable will be expanded independent of /e, as such is the nature of the s operator.

 
___crazyinsomniac_______________________________________
Disclaimer: Don't blame. It came from inside the void
perl -e "$q=$_;map({chr unpack qq;H*;,$_}split(q;;,q*H*));print;$q/$q;"

If you are into a heavy duty Text pre-processor, you could use Text::Vpp.
It allows you even such fancy things like perl code being processed while you are doing your preprocessing which will give you the possibility of doing things like:

if($gender == 'f') {
 Dear Mrs. $name,
} else {
 Dear Mr. $name,
}

we would like to invite you...
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Bye
 PetaMem

my $text = << 'end_of_test';
Your child <child> is invited to
come to our school.  Your child's
teacher will be <teacher>, and the
class is held in <room>.";
end_of_test

my %hash = ('child' => 'mary',
            'teacher' => 'mrs b',
            'room' => '123');

print "Raw: $test\n";

$test =~
  s[<(\w+)>]
   [defined($hash{$1}) ? $hash{$1} : warn]ieg;

print "Processed: $test\n";
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foreach (0..@ChildName - 1) {
    my $text = "Your child $ChildName[$_] is invited to
      come to our school. Your child's teacher will be
      $TeacherName[$_], and the class is held in room
      $RoomNo[$_].";
    &PrintNotice($text) # or whatever...
}
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Because this isn't within a script - I'm basically allowing users to create their own paragraph-like ouput of database rows. I wanted to have the combination of ease of use for non-savvy users, and ease of me translating the text into the right thing. I might convert to using <> instead of ##. ## is kinda useful because it's the way that some (like Cold Fusion) user-friendly systems use for variables.

mitd-Made in the Dark
'My favourite colour appears to be grey.'

my $rhChildren = {
   {'Peter'} => {
      child_name => 'Peter',
      teacher_name => 'Ms. Jones',
      room_number => '503'
   }
};   #add records as needed

my $text = "Your child #child_name# is invited to come to our school. 
+Your child's teacher will be #teacher_name#, and the class is held in
+ room #room_number.";

foreach my $child (keys %$rhChildren) {
   my $substText;
   ($substText = $text) =~ s/\#([^#]+)\#/$rhChildren->{$child}{$1}/g;
   print "$substText\n";
}
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OK, so there is a redundancy in using the child's name both as key and value in the hash, but it works and uses regexes, right?

The previous examples either ignore greedy matching or attempt to to emulate it. I believe this is what you're looking for:

$text =~ s/#(\w+?)#/$hash{$1}/g;

That would be a problem if \w included the octothorpe. It doesn't, so it's not a problem.