$baz = "mythingie";
($foo, $bar) = $baz =~ s/(my)(.*)//;

##</code><code>##

use strict; 
$baz = 'mythingie';
if($baz =~ s/(my)(.*)//){  
#s/// returns '' (which is false) if it doesn't match.  
#No, I don't know why it doesn't return 0.
  $foo = $1;
  $bar = $2;
} else {
  warn 'I thought this would always match, but I must be wrong';
}