perl-5.26.1
study SCALAR
study

At this time, study does nothing. This may change in the future.

現時点では、study は何もしません。 これは将来変更されるかもしれません。

Prior to Perl version 5.16, it would create an inverted index of all characters that occurred in the given SCALAR (or $_ if unspecified). When matching a pattern, the rarest character from the pattern would be looked up in this index. Rarity was based on some static frequency tables constructed from some C programs and English text.

Perl バージョン 5.16 より前では、 it would create an inverted index of all characters that occurred in the given SCALAR (or $_ if unspecified). When matching a pattern, the rarest character from the pattern would be looked up in this index. Rarity was based on some static frequency tables constructed from some C programs and English text. (TBT)