x= , the repetition assignment operator, only works on scalars.

So you can do: 

my $str = 'ab';
$str x= 2;
print $str;
# 'abab'

[download]

You don't say what you want as output, but maybe you are looking for: 
#!/usr/bin/perl

use warnings;
use strict;

$\ = $/;

@_ =  ( 'a' .. 'b' ) x 2;
print for @_;

[download]
Output: 
a
b
a
b

[download]
edit: show example of repetition assignment on a scalar
The way forward always starts with a minimal test.

In reply to Re: ... for (@_) x= 2; by 1nickt
in thread ... for (@_) x= 2; by rsFalse

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