s///, s//// for $v

substitute-for-loop.pl

#!/usr/bin/env perl
# Captured $1 vs. ${^MATCH}
use strict;
use warnings;
use Benchmark ':all';
use Test::More 'no_plan';

my $q = ' neko nyaan cat ';
sub s3 {
    my $v = shift;
    $v =~ s/\A //;
    $v =~ s/ \z//;
    $v =~ s/ /-/g;
    return $v;
}

sub s4 {
    my $v = shift;
    s/\A //, s/ \z//, s/ /-/g for $v;
    return $v;
}

is s3($q), 'neko-nyaan-cat';
is s4($q), 'neko-nyaan-cat';

printf("Running with Perl %s on %s\n%s\n", $^V, $^O, '-' x 80);
cmpthese(6e6, {
        's/...// x 3' => sub { s3($q) },
        's/...// for' => sub { s4($q) },
    }
);

__END__
Running with Perl v5.30.0 on darwin
--------------------------------------------------------------------------------
                Rate s/...// x 3 s/...// for
s/...// x 3 454201/s          --         -6%
s/...// for 483092/s          6%          --

Running with Perl v5.32.0 on darwin
--------------------------------------------------------------------------------
                Rate s/...// x 3 s/...// for
s/...// x 3 456274/s          --         -3%
s/...// for 469116/s          3%          --