why it is working when I called the function without argument

Presumably because \&function (without parentheses) is a reference to the function, while \&function(...) is a reference to whatever the called function returned. 

#!/usr/bin/perl -l

sub function {
    return "foo";
}

$command = \&function;
print $command;

$command = \&function();
print "$command -> $$command";

__END__
$ ./833005.pl
CODE(0x604fd0)
SCALAR(0x604290) -> foo

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In reply to Re^3: Perl/TK : Passing arguments to the function while clicking submit button by almut
in thread Perl/TK : Passing arguments to the function while clicking submit button by kiruthika.bkite

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