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Perl Language Reference Manual
by Larry Wall and others
Paperback (6"x9"), 724 pages
ISBN 9781906966027
RRP £29.95 ($39.95)

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The version + patchlevel / 1000 of the Perl interpreter. This variable can be used to determine whether the Perl interpreter executing a script is in the right range of versions. (Mnemonic: Is this version of perl in the right bracket?) Example:

warn "No checksumming!\n" if $] < 3.019;

See also the documentation of use VERSION and require VERSION for a convenient way to fail if the running Perl interpreter is too old.

The floating point representation can sometimes lead to inaccurate numeric comparisons. See $^V for a more modern representation of the Perl version that allows accurate string comparisons.

ISBN 9781906966027Perl Language Reference ManualSee the print edition