Can you grep and remove simultaneously?

I don't think so... I tried:

  my @A = grep m/A/ && !defined($_ = undef), @foo ;
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The following at least works:

  use strict ;
  use warnings ;

  my @foo = ('A', 'B', 'C', 'A', 'B', 'A', 'D') ;

  my $q ;
  my @A = map defined($_) && m/A/ ? scalar($q = $_, $_ = undef, $q) : 
+(), @foo ;
  my @B = map defined($_) && m/B/ ? scalar($q = $_, $_ = undef, $q) : 
+(), @foo ;
  my @C = map defined($_) && m/C/ ? scalar($q = $_, $_ = undef, $q) : 
+(), @foo ;

  @foo = grep defined($_), @foo ;

  print "A: @A\n" ;
  print "B: @B\n" ;
  print "C: @C\n" ;
  print "   @foo\n" ;
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