$ perl -Mre=debug -e " $_ = 1234; m/.$/ "
Compiling REx ".$"
Final program:
   1: REG_ANY (2)
   2: EOL (3)
   3: END (0)
anchored ""$ at 1 minlen 1
Matching REx ".$" against "1234"
   3 <123> <4>               |  1:REG_ANY(2)
   4 <1234> <>               |  2:EOL(3)
   4 <1234> <>               |  3:END(0)
Match successful!
Freeing REx: ".$"

$ perl -Mre=debug -e " $_ = 1234; m'.$' "
Compiling REx ".$"
Final program:
   1: REG_ANY (2)
   2: EOL (3)
   3: END (0)
anchored ""$ at 1 minlen 1
Matching REx ".$" against "1234"
   3 <123> <4>               |  1:REG_ANY(2)
   4 <1234> <>               |  2:EOL(3)
   4 <1234> <>               |  3:END(0)
Match successful!
Freeing REx: ".$"