Win8 Strawberry 5.30.3.1 (64)  Tue 06/07/2022 17:48:45
C:\@Work\Perl\monks
>perl

use 5.010;
use strict;
use warnings;

use constant {
    PATH    => 0,
    VERSION => 1,
    WANT    => 2,
};

use Benchmark 'cmpthese';
use Test::More;

my @tests = (
    # version found
    [qw{
        /a/b/version1/c/d
        version1
        /a/b/version1
    }],
    # version found
    [qw{
        /some/path/3.5.2+tcl-tk-8.5.18+sqlite-3.10.0/a/b/c
        3.5.2+tcl-tk-8.5.18+sqlite-3.10.0
        /some/path/3.5.2+tcl-tk-8.5.18+sqlite-3.10.0
    }],
    # version not found - no change in path
    [qw{
        /some/path/3.5.2+tcl-tk-8.5.18+sqlite-3.10.0/a/b/c
        9.9.9
        /some/path/3.5.2+tcl-tk-8.5.18+sqlite-3.10.0/a/b/c
    }],
);

plan tests => 2*@tests;

for my $test (@tests) {
    is _regex (@$test[PATH, VERSION]), $test->[WANT];
    is _rindex(@$test[PATH, VERSION]), $test->[WANT];
}

cmpthese 0 => {
    regex0  => sub { _regex  (@{$tests[0]}[PATH, VERSION]); },
    regex1  => sub { _regex  (@{$tests[1]}[PATH, VERSION]); },
    regex2  => sub { _regex  (@{$tests[2]}[PATH, VERSION]); },
    rindex0 => sub { _rindex (@{$tests[0]}[PATH, VERSION]); },
    rindex1 => sub { _rindex (@{$tests[1]}[PATH, VERSION]); },
    rindex2 => sub { _rindex (@{$tests[2]}[PATH, VERSION]); },
};

sub _regex {
    my ($path, $version) = @_;

    $path =~ s/.*\Q$version\E\K.*//s;

    return $path;
}

my $r_offset;  # variable creation excluded from timing

sub _rindex {
    my ($path, $version) = @_;

    return ($r_offset = rindex $path, $version) >= 0
         ? substr $path, 0, $r_offset + length $version
         : $path  # version not found: return path unchanged
         ;

}

# sub _rindex {
#     my ($path, $version) = @_;
#
#     return $path unless ($r_offset = rindex $path, $version) >= 0;
#     return substr $path, 0, $r_offset + length $version;
#
# }

# sub _rindex {  # fails if version not found
#     my ($path, $version) = @_;
#
#     $path = substr $path, 0, length($version) + rindex $path, $version;
#
#     return $path;
# }

^Z
1..6
ok 1
ok 2
ok 3
ok 4
ok 5
ok 6
            Rate  regex1  regex0  regex2 rindex1 rindex0 rindex2
regex1  104916/s      --     -5%    -52%    -83%    -84%    -88%
regex0  109922/s      5%      --    -49%    -82%    -83%    -88%
regex2  217207/s    107%     98%      --    -64%    -66%    -76%
rindex1 602123/s    474%    448%    177%      --     -6%    -33%
rindex0 641287/s    511%    483%    195%      7%      --    -29%
rindex2 899759/s    758%    719%    314%     49%     40%      --