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use strict; use warnings; ... } say +( $str =~ tr/1/1/ ) / $len;
$ perl 171126.pl 0.4988 0.00312
$ perl -v This is perl 5, version 26, subversion 0 (v5.26.0) built for x86_64-li +nux-thread-multi (with 1 registered patch, see perl -V for more detail)