Using a simple Benchmark example:

$ perl -le'
use Benchmark q/cmpthese/;
my @data = map { join( "", map { ( "a" .. "z" )[ rand 26 ] } 1 .. 10 +
+ rand( 10 ) ) . "\n" } 1 .. 1_000;
cmpthese -10, {
    plus => sub {
        my @temp = @data;
        s/\s+$// for @temp;
        return @temp;
        },
    star => sub {
        my @temp = @data;
        s/\s*$// for @temp;
        return @temp;
        }
    }
'
      Rate star plus
star 336/s   -- -66%
plus 992/s 196%   --

$ perl -le'
use Benchmark q/cmpthese/;
my @data = map { join( "", map { ( "a" .. "z" )[ rand 26 ] } 1 .. 10 +
+ rand( 10 ) ) . "" } 1 .. 1_000;
cmpthese -10, {
    plus => sub {
        my @temp = @data;
        s/\s+$// for @temp;
        return @temp;
        },
    star => sub {
        my @temp = @data;
        s/\s*$// for @temp;
        return @temp;
        }
    }
'
       Rate star plus
star  334/s   -- -72%
plus 1211/s 263%   --
[download]

It appears that \s+ is always faster than \s*.     YMMV