The only thing I can think is that when you have quote marks the string as a whole contains "shell metacharacters", and when you don't, it doesn't.

For example, see this bit from the documentation for perl's system command:

If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing (this is "/bin/sh -c" on Unix platforms, but varies on other platforms). If there are no shell metacharacters in the argument, it is split into words and passed directly to "execvp", which is more efficient.

#!perl
$ENV{CLASSPATH}="/usr/work/ticket/ETicketClient.jar:.";
print "Without shell metachars we get:\n",
      grep(/CLASSPATH/, qx[/usr/bin/env]), "\n";
print "With shell metachars we get:\n", 
      grep(/CLASSPATH/, qx[/bin/false || /usr/bin/env]), "\n";
[download]

See if there's a difference in the two outputs.

So then, the question is, why is this clearing the environment? It's not supposed to, but I wonder if on your system /bin/sh is aliased to csh. (or if perhaps the qx[] operator uses your default shell, which might be csh) Csh has a habit of always running its initialization scripts even if it's just being called for one command, and that could reset your environment variable settings.

Fortunately, for java there is a simple solution - you can change your original code to:

#!/usr/bin/perl -w 
my $cp = "/usr/work/ticket/ETicketClient.jar:."; 
$ENV{PATH}.=":/usr/work/ticket/" 
$test="This is perl ticket"; 
my $result =qx/java -cp \Q$cp\E ETicket.ETicketClient -i TICKET -n  p_
+name -t "\Q$test\E"/; 
print $result;
[download]

@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/
[download]