Due to the way the single-quote string constructor handles backslashes (escapes), the \\ will in this case compile to a single literal backslash. See Quote and Quote-like Operators and the discussion of q/STRING/ in Quote-Like Operators.

Thanks for your comment, AM. Your link is a good read and worth reposting. I thought that the collapsing of backslashes was done by the OS in resolving paths. I was unaware that perl did it.

do you dispute that there is a left-curly (and a right-curly) in the \x{A3f4} string? What else would you call it/them?

I do not dispute that, so this string itself never represents a left curly brace, rather it has a left curly brace in it.

I would call it (or in this case \x{A3f4}) "the string compiled from '\\x{A3f4}'"

Ok. From the above source we have:

\x{263A}     [1,8]  hex char          (example shown: SMILEY)
\x{ 263A }          Same, but shows optional blanks inside and
                    adjoining the braces
\x1b         [2,8]  restricted range hex char (example: ESC)

[download]

So, I think "aha, it's a hex representation", but then I can't get there with the REPL:

  DB<1> $str2='\\x{263}'                                              
+          

  DB<2> p $str2                                                       
+          
\x{263}
  DB<3> p hex $str2                                                   
+          
0
  DB<4> print hex $str2                                               
+          
0

[download]

I would expect to see a smiley face rather than zero. This is a head-scratcher:

DB<6> $str3='\\\\\\\x{aF}'                                            
+        

  DB<7> p $str3                                                       
+          
\\\\x{aF}
  DB<8> p hex $str3                                                   
+          
0
  DB<9> print hex $str3                                               
+          
0

[download]

$str3 goes from 7 to 4 backslashes when compiled(?). But I get zero for a hex value no matter what I try:

  DB<10> $str4='\x{aF}'                                               
+          

  DB<11> p $str4                                                      
+          
\x{aF}
  DB<12> print hex $str4                                              
+          
0
  DB<13> print hex 'aF'                                               
+          
175

[download]

How do I tease 175 out of $str4?

The \x part has nothing to do with the /x or /xx regex modifiers.

That part is clearer now. I have that backslash/forwardslash disphoria going on now where I can hardly see the difference and it looks like a toothpick war. I get the occasional billiken that I read or write the wrong way.

In reply to Re^6: Unescaped left brace in regex is passed through in regex by Aldebaran
in thread Unescaped left brace in regex is passed through in regex by gzh

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