... it breaks $1 and m//atching operator ... No warnings are issued, matching is broken in a different scope ...

It certainly aliases  $1 and this is certainly not a good idea, but matching is not broken. (Please see example code below.) A match is made properly and the truth of the match is returned. The content of capture group 1 cannot be directly accessed (because the  $1 symbol has been aliased to something else), but the content of this group is still proper and can be accessed indirectly if a kind of "preemptive strike" aliasing of  $1 (or rather of the data it symbolizes) has been done. Other variables associated with this group still function as expected. I don't see your point about matching in a different scope (which I take to mean outside the scope of the for-loop alias) being broken; again, see code below. As to warnings... well, as weird as this (ab)use of  $1 is, in programmng as in life, it's just not possible to warn about all the weird things one might do; at some point one must fall back upon common sense. 

c:\@Work\Perl\monks>perl -wMstrict -le
"for my $one ($1) {
   $_ = 'xx333333xx';
   for $1 (666) {
     print qq{A: '$one' $-[1] $+[1]  '$2'} if /(333)\1(xx)/;
     print qq{\$1 '$1'};
     }
   }
 ;;
 print qq{B: '$1' $-[1] $+[1]  '$2'} if /(\d\d\d)\1(\D\D)/;
"
A: '333' 2 5  'xx'
$1 '666'
B: '333' 2 5  'xx'

[download]

Bottom line: This is just the way aliasing works (insofar as I understand it), but you don't have to use something just because it works. Again, common sense.

Give a man a fish:  <%-(-(-(-<

In reply to Re^8: Getting an unknown error (foreach $1 breaks m//atch) by AnomalousMonk
in thread Getting an unknown error by andybshaker

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