DB<138> $_="  x1x2x3x  x4x5x"
 => "  x1x2x3x  x4x5x"

  DB<139> ; /x(\d)x(?{print "<$1>\t"})(?!)/
<1>	<2>	<3>	<4>	<5>	

##</code><code>##

  DB<154> while ( /x(\d)x/g ) { print $1; pos($_) -= length($ &)-1 }
12345