You are viewing the version of this documentation from Perl 5.40.0-RC2. This is a development version of Perl.
study SCALAR

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

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.