in reply to Two variables changed by tr

foreach aliases into the list rather than copying. As you have 2 nested loops over the same array, half the time your two lexicals are aliases for the same item in the array.

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Re^2: Two variables changed by tr
by glendeni (Sexton) on Jul 03, 2024 at 19:45 UTC
    Thanks - learned something new today
[reply]
      Compare: 
      use warnings;
use strict;
my @chars = ( 'a', 'b' ) ;
foreach my $char1 ( @chars )
{
  foreach my $char2 ( @chars )
  {
    print "BEFORE: $chars[0] $chars[1] \n" ;
    $char2 =~ tr/a-z/A-Z/ ;  # $char1 ALSO UPPER-CASED !?
    print " AFTER: $chars[0] $chars[1] \n" ;
  }
}

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Re^2: Two variables changed by tr
by ikegami (Patriarch) on Jul 04, 2024 at 16:20 UTC

    Example: 

    my @chars = qw( a b c );

for my $char ( @chars ) {
   $char = uc( $char );
}

say "@chars";  # A B C

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