your code section is hard to decipher in my chrome

> 

 if ($str =~ /(\\x{[A-F\d]+})/i){    // error by perl -Tcw

 if ($str =~ /^(\d{2,4})[^\d](\d{2})/){     // no error by perl -Tcw

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some remarks:

  1. you don't append comments with // in Perl, it's #
  2. the no error part is legal syntax for a a range of repetitions
  3. the error part is not, hence (old) Perl thinks ° a literal curly { is expected. so implicitly { is translated to \{ instead of throwing an error
  4. the deprecation means that literal { has to be escaped explicitly now

Please note the difference:

(debugger demo with perl -de0 )

DB<4> $str =  '\\x{A3f4}'                                           # 
+literal curly

DB<5> if ( $str =~ /(\\x{[A-F\d]+})/i ) { print $1 }                # 
+implicit but deprecated                                            
\x{A3f4}     

DB<6> use warnings; if ( $str =~ /(\\x\{[A-F\d]+})/i ) { print $1 } # 
+explicit and no warning 
\x{A3f4}     

DB<7> $str =  '123X12'                                              # 
+no curlies, just repeated numbers

DB<8> if ( $str =~ /^(\d{2,4})[^\d](\d{2})/) { print "$1;$2" }      # 
+meta curly
123;12

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

°) see DWIM

In reply to Re^3: Unescaped left brace in regex is passed through in regex by LanX
in thread Unescaped left brace in regex is passed through in regex by gzh

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