$INPUT_RECORD_SEPARATOR

$= The current page length (printable lines) of the currently selected output channel. The default is 60. Mnemonic:

$FORMAT_FORMFEED

$MATCH

%^H The %^H hash provides the same scoping semantic as

$^W The current value of the warning switch, initially true if -w was used, false otherwise, but directly modifiable.

$0 Contains the name of the program being executed. On some (but not all) operating systems assigning to

$WARNING

${^LAST_FH} This read-only variable contains a reference to the last-read filehandle. This is set by

${^OPEN} An internal variable used by PerlIO. A string in two parts, separated by a \0 byte