D:\>perl -E"my $x; BEGIN{$x=qr/a.*u/}; use re 'debug'; my $str = 'aou'; say $str
 =~ /$x$x/"
Compiling REx "(?^u:a.*u)(?^u:a.*u)"
Final program:
   1: EXACT <a> (3)
   3: STAR (5)
   4:   REG_ANY (0)
   5: EXACT <ua> (9)
   9: STAR (11)
  10:   REG_ANY (0)
  11: EXACT <u> (13)
  13: END (0)
anchored "a" at 0..0 floating "ua" at 1..9223372036854775807 (checking floating)
 minlen 4
String shorter than min possible regex match (3 < 4)

Freeing REx: "(?^u:a.*u)(?^u:a.*u)"