DB<109> $pattern='abcdabcdabce'
 => "abcdabcdabce"

  DB<110> $n=2,$k=2
 => (2, 2)

  DB<111> $str = ($pattern x $n ) . substr($pattern,0,$k) 
 => "abcdabcdabceabcdabcdabceab"

  DB<112> $str eq 'abcdabcdabceabcdabcdabceab'
 => 1