$ perl -Mre=debug -e " $f = qr/./; warn if m/$f/"
Compiling REx "."
Final program:
   1: REG_ANY (2)
   2: END (0)
minlen 1
Freeing REx: "."

$ perl -Mre=debug -e " $f = qr/./; $g = qr/$f/; warn if m/$g/"
Compiling REx "."
Final program:
   1: REG_ANY (2)
   2: END (0)
minlen 1
Freeing REx: "."
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$ perl -Mre=debug -e " $f = qr/./; $g = qr/./; $c=qr/$f$g/; "
Compiling REx "."
Final program:
   1: REG_ANY (2)
   2: END (0)
minlen 1
Compiling REx "."
Final program:
   1: REG_ANY (2)
   2: END (0)
minlen 1
Compiling REx "(?-xism:.)(?-xism:.)"
Final program:
   1: REG_ANY (2)
   2: REG_ANY (3)
   3: END (0)
minlen 2
Freeing REx: "."
Freeing REx: "."
Freeing REx: "(?-xism:.)(?-xism:.)"
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