chomp(@slurp = <>);
print @slurp;
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$text = do { local $/; <>};
$text =~ s/\n//g;                  # for some \n
print $text;
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And a requisite, ill-advised and derivative one-liner:

my $slomped = join "", do { local $/; <>} =~ m/([^\n]+)/g;

It's slower, messier, and hard to read. On the plus-side, I'd like to coin the term 'slomped'.

That's ok, if you allow me to claim to the term "chumped" ;-)

---

Remember rule one...

I can never be bothered to remember how to slurp files. And I don't have to because File::Slurp remembers for me.

use File::Slurp;
my $data = File::Slurp::read_file('filename');
$data =~ s/\015?\012//g;
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Some people will wonder why I bother to use a module to handle a concept that can be written in only a couple lines of code, but I know that File::Slurp will always 'Do the Right Thing', whereas I have been known to make silly little mistakes (I always used to get $| confused with $/).

my $out;
while (<>) {
  chomp;
  $out .= $_;
}
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How about this: Perl Idioms Explained - my $string = do { local $/; <FILEHANDLE> }; ?

UPDATE:
Oh ... you want to remove the newlines ... well, you could remove the newlines with a simple regex:

$string =~ s/\n//g;
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$string =~ s/\n/ /g;
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L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

The reason your multiChomp fails is because you are setting @out from $_, instead of from @_; it is the latter that holds the arguments to the function.

Just a couple of observations. One is that you don't need the loop in multiChomp; you can achieve the exact same results with chomp @out. Also, I don't see the utility of chomping the entire array and then returning only the first chomped element, which is what multiChomp does in scalar context. A more useful thing would be to return the concatenation of the chomped elements. Taken all this together, I would rewrite multiChomp like this:

sub multiChomp {
  my @out = @_;
  chomp @out;
  return wantarray ? @out : join '', @out;
}
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Or you could do this:

( my $text = do { local $/, @ARGV = 'foo.txt'; <> } ) =~ s/\n+//g;
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    while (<$messageHandle>)
    {
        chomp;
        $body .= $_;
    }
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use strict;
use warnings;

$_ = join '',<DATA>; s/\n//g;
print;

__DATA__
line 1
line 2
line 3
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