perlmod| perldoc.perl.org
perlobj| perldoc.perl.org
A file test, where X is one of the letters listed below. This unary operator takes one argument, either a filename, a filehandle, or a dirhandle, and tests the associated file to see if something is true about it. If the argument is omitted, tests $_, except for -t, which tests STDIN. Unless otherwise documented, it returns 1 for true and '' for false. If the file doesn't exist or can't be examined, it returns undef and sets $! (errno). With the exception of the -l test they all follow symbol...| perldoc.perl.org
perlclass| perldoc.perl.org