Re^2: Misreading m// documentation (BUG?)

> If "'" is the delimiter, no interpolation is performed on the PATTERN.

hmm, strange in 5.10 this uncommon feature seems to be buggy:

$ perl
if ( '_$x_' =~ '$x') { print "match 1" }                      
if ( '_$x_' =~ /\$x/){ print "match 2" }
__DATA__
match 2
[download]

while B::Deparse claims both lines to be identical ...

perl -MO=Deparse 
if ( '_$x_' =~ '$x') { print "match 1" }                      
if ( '_$x_' =~ /\$x/){ print "match 2" }
__DATA__
if ('_$x_' =~ /\$x/) {
    print 'match 1';
}
if ('_$x_' =~ /\$x/) {
    print 'match 2';
}
__DATA__
- syntax OK
[download]

... does B::Concise show that the interpolation is not inhibited

perl -MO=Concise
if ( '_$x_' =~ '$x') { print "match 1" }                      
if ( '_$x_' =~ /\$x/){ print "match 2" }
__DATA__
g  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 3 -:1) v:{ ->3
-     <1> null vKP/1 ->9
5        <|> and(other->6) vK/1 ->9
4           </> match(/"$x"/) sKS/RTIME ->5              <-- INTERPOLA
+TED
3              <$> const[PV "_$x_"] s ->4
-           <@> scope vK ->-
-              <0> ex-nextstate v ->6
8              <@> print vK ->9
6                 <0> pushmark s ->7
7                 <$> const[PV "match 1"] s ->8
9     <;> nextstate(main 5 -:2) v:{ ->a
-     <1> null vKP/1 ->g
c        <|> and(other->d) vK/1 ->g
b           </> match(/"\\$x"/) sKS/RTIME ->c            <-- NO INTERP
+OLATION
a              <$> const[PV "_$x_"] s ->b
-           <@> scope vK ->-
-              <0> ex-nextstate v ->d
f              <@> print vK ->g
d                 <0> pushmark s ->e
e                 <$> const[PV "match 2"] s ->f
- syntax OK
[download]

added marks to highlight differences.

Can someone please check for other perl versions?

Cheers Rolf

( addicted to the Perl Programming Language)

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Re^3: Misreading m// documentation (BUG?) by ikegami (Patriarch) on Mar 12, 2014 at 15:06 UTC
Bug in Deparse. Still present. The regex pattern is `$x # End of line followed by "x"` [download] so the literal should be `m'$x'` [download] It's the only match operator that will produce exactly that regex pattern.	[reply] [d/l] [select]
Re^3: Misreading m// documentation (BUG?) by Anonymous Monk on Mar 12, 2014 at 12:16 UTC
shorter example interpolation, the \Q\E is interpolated in double quoted strings `$ perl -Mre=debug -e " $f=q{a??q}; $f =~ m{\Qa??\E}; " Compiling REx "a\?\?" Final program: 1: EXACT <a??> (3) 3: END (0) anchored "a??" at 0 (checking anchored isall) minlen 3 Guessing start of match in sv for REx "a\?\?" against "a??q" Found anchored substr "a??" at offset 0... Guessed: match at offset 0 Freeing REx: "a\?\?"` [download] use qr to see how \Q\E gets interpolated `$ perl -le " print qr{\Qa??\E}; " (?^:a\?\?)` [download] without interpolation the pattern is completely different `$ perl -le " print qr'\Qa??\E'; " (?^:\Qa??\E)` [download] The regex metacharcters are still regex metacharacters (pattern) `$ perl -Mre=debug -e " $f=q{a??q}; $f =~ m'\Qa??\E'; " Compiling REx "\Qa??\E" Final program: 1: EXACT <Q> (3) 3: MINMOD (4) 4: CURLY {0,1} (8) 6: EXACT <a> (0) 8: EXACT <E> (10) 10: END (0) anchored "Q" at 0 floating "E" at 1..2 (checking floating) minlen 2 Guessing start of match in sv for REx "\Qa??\E" against "a??q" Did not find floating substr "E"... Match rejected by optimizer Freeing REx: "\Qa??\E"` [download] perlrebackslash :)	[reply] [d/l] [select]
Re^4: Misreading m// documentation (BUG?) by LanX (Saint) on Mar 12, 2014 at 13:48 UTC
Probably you are right, I'm, still too decaffeinated to tell! ;-) But then B::Deparse is buggy. Cheers Rolf ( addicted to the Perl Programming Language)	[reply]
Re^3: Misreading m// documentation (BUG?) by Anonymous Monk on Mar 12, 2014 at 12:00 UTC
Um, $ is still a metacharacter, try '\$x'	[reply]
Re^4: Misreading m// documentation (BUG?) by LanX (Saint) on Mar 12, 2014 at 12:03 UTC
> Um, $ is still a metacharacter, try '\$x' If `"'"` is the delimiter, no interpolation is performed on the PATTERN. Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l]
Re^5: Misreading m// documentation (BUG?) by Anonymous Monk on Mar 12, 2014 at 12:07 UTC
Yes, interpolation means double quoted string, regex metacharacters are still regex metacharacters m/.$/ and m'.$' match the same string Read more... (1094 Bytes) variables interpolate in double quoted strings but metachars are still metachars Read more... (2 kB)	[reply] [d/l] [select]