Since the two-character literal sequence  '\v' (backslash, "v") seems to be the fly in the ointment, why not handle it as the sole exceptional case? The code is simpler, but still needs substitution replacement  /e code evaluation involving an eval and I've done no Benchmark-ing to see if it's actually faster; it always pays to be suspicious when  /e or eval are involved. 

>perl -wMstrict -le
"use Test::More 'no_plan';
 use Test::NoWarnings;
 ;;
 my $s =
   join '',
   map  qq{$_\\$_$_\\$_\\$_$_},
   qw(r n b a f t v)
   ;
 my $o =
   join '', 'x',
   map  qq{\\${_}y\\$_\\${_}x},
   qw(0 7 10 77 100 377)
   ;
 print qq{'$s'};
 print qq{'$o'};
 print '';
 ;;
 for ($s, $o) {
   s{ ( \\ (?: [0-7]{1,3} | [rnbaft])) | \\v }
    { $1 ? eval qq{qq{$1}} : qq{\013}        }xmsge;
   }
 print raw_hex($s);
 print raw_hex($o);
 print '';
 ;;
 ok $s eq qq{r\rr\r\rrn\nn\n\nnb\bb\b\bba\aa\a\aaf\ff\f\fft\tt\t\ttv\0
+13v\013\013v};
 ok $o eq qq{x\000y\000\000x\007y\007\007x\010y\010\010x\077y\077\077x
+\100y\100\100x\377y\377\377x};
 ;;
 ;;
 sub raw_hex { return join ' ', unpack '(H2)*', $_[0]; }
"
'r\rr\r\rrn\nn\n\nnb\bb\b\bba\aa\a\aaf\ff\f\fft\tt\t\ttv\vv\v\vv'
'x\0y\0\0x\7y\7\7x\10y\10\10x\77y\77\77x\100y\100\100x\377y\377\377x'

72 0d 72 0d 0d 72 6e 0a 6e 0a 0a 6e 62 08 62 08 08 62 61 07 61 07 07 6
+1 66 0c 66 0c 0c 66 74 09 74 09 09 74 76 0b 76 0b 0b 76
78 00 79 00 00 78 07 79 07 07 78 08 79 08 08 78 3f 79 3f 3f 78 40 79 4
+0 40 78 ff 79 ff ff 78

ok 1
ok 2
ok 3 - no warnings
1..3

[download]

In reply to Re: C strings, unescaping of by AnomalousMonk
in thread C strings, unescaping of by Anonymous Monk

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