predefined variables - a partial list
$| or $OUTPUT_AUTOFLUSH
- By default, all Perl output is buffered (0). To enable automatic flushing, set this variable to 1. Needed when doing MPE I/O which is usually unbuffered.
$$ or $PID
- POSIX PID of the current process
$^O or $OSNAME
- operating system name (mpeix)
%ENV or $ENV{varname}
- accesses the POSIX environment variables