Re^3: Compiled regular expression using qr

In the OP and in your reply above, you use the terms "exact" and "case insensitive" in the context of regex matching in a way that leads me to wonder if you understand that case insensitive matching is inherently inexact. E.g.:

c:\@Work\Perl>perl -wMstrict -le
"my $rx = qr/^data_123$/i;
 print $rx;
 ;;
 for my $s (qw(data_123 DATA_123 dAtA_123  data_123x data_12 nada_123)
+) {
   if ($s =~ $rx) {
     print qq{'exact' match to '$s'};
     }
   else {
     print qq{NO match to '$s'};
     }
   }
"
(?^i:^data_123$)
'exact' match to 'data_123'
'exact' match to 'DATA_123'
'exact' match to 'dAtA_123'
NO match to 'data_123x'
NO match to 'data_12'
NO match to 'nada_123'
[download]

Update: I should have mentioned that the example above was run under Strawberry Perl version 5.14.4.1.

Comment on Re^3: Compiled regular expression using qr Download Code

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Re^4: Compiled regular expression using qr by perlbaski (Sexton) on Oct 15, 2014 at 22:32 UTC
My bad, I reinitialized the variable as part of debugging, no wonder it would not match. Thanks for clarifying on its use. That said, the stringify version has ?^ in front, I know that ? means 0 or more of the chars preceding it, but what does ?^ mean?	[reply]
Re^5: Compiled regular expression using qr by AnomalousMonk (Archbishop) on Oct 15, 2014 at 23:54 UTC
A stringized regex object is wrapped in a non-capturing grouping that preserves the regex modifiers in effect when the regex was compiled. This allows a regex object to be unaffected by the modifiers in effect in any enclosing regex 'scope' during interpolation within another regex or regex object. Consider: `c:\@Work\Perl>perl -wMstrict -le "my $rx = qr/(?^xms:^data_123$)/; print $rx; ;; my $ry = qr/^data_123$/xms; print $ry; ;; my $rz = qr{ T $rx U $ry V }xms; print $rz; " (?^:(?^xms:^data_123$)) (?^msx:^data_123$) (?^msx: T (?^:(?^xms:^data_123$)) U (?^msx:^data_123$) V )` [download] See also the discussion of `"(?^aluimsx:pattern)"` in the Extended Patterns section of perlre.	[reply] [d/l] [select]
Re^5: Compiled regular expression using qr by ikegami (Patriarch) on Oct 15, 2014 at 23:05 UTC
`?^` is garbage. `(?^i:...)`, on the other hand, means that the pattern within should be matched case-insensitively as you requested.	[reply] [d/l] [select]