use IPC::Open3;

sub backticks {
  my $pid = open3(my $wfh, my $rfh, 0, @_)
              or die "open3 failed: $!";
  close($wfh); # assume the script needs no input
  my $output;
  while (<$rfh>) { $output .= $_ }
  close($rfh);
  $output;
}

my $java_output = backticks('java', '--classpath=...', ...);
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No need for open3.

sub backticks {
  open(my $pipe, '-|', @_)
     or return;
  local $/ = wantarray ? $/ : undef;
  <$pipe>
}

my $java_output = backticks('java', '--classpath=...', ...);
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Bonus: Handles context and errors just like the real thing.

Is this available in a standard module? If not, I think it should be. The situation seems to comes up enough. I'd like to deprecate all calls to exec which invoke an intermediate shell and replace them with safer alternatives.

Update: Banning all use of the single-argument forms of exec, system, etc. is probably too draconian. The real problem occurs when a variable is interpolated in that single argument, e.g. my $output = `command $arg`. Perhaps this is something that Perl::Critic can look for and advise that a safer way should be sought to perform the operation.

$ENV{CLASSPATH} = ...;
my $output = `java ...`; # no need to specify -classpath here
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Thanks all for responding. The error given by java was actually misleading. Though the error mentioned ClassNotFound, the actual issue was in one of the command line parameters which also had a space in it. When I put that in quotes, I got the expected behaviour.

the actual issue was in one of the command line parameters which also had a space in it.

We know. That's what all the solutions we provided addressed. Adding quotes is actually a rather poor solution. The solutions provided go beyond adding quotes and avoid the need for quoting and escaping completely. That's much safer and reliable.